Archive February 2012

videos on creationism & evolution Alison Campbell Feb 29

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A while back, I wrote about the way that the geology of the Grand Canyon has been misrepresented by ‘Young Earth’ creationists. Now here’s a good discussion of this from geologist Steve Newton:

You may also remember the comments about evolution that were made by some of last year’s Miss USA contestants. A 2012 Darwin Day talk by Josh Rosenau looks at how closely the contestants’ views match those of Americans in general. His context is the continuing efforts to see various ‘flavours’ of creationism taught in science classrooms.

Both are interesting viewing & could form the basis of some good classroom discussion :-)

cute, creative caminalcules Alison Campbell Feb 28

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This post was originally written for Talking Teaching, where it has the title “what is the caminalcule lab supposed to teach?” You can get some good ideas for posts from reading the search terms that bring people to your site :-)

I was first introduced to the Caminalcules way back in the dim dark past when I was a brand new undergraduate student. They were the basis of a lab exercise on evolution & evolutionary relationships, & were invented by the taxonomist Joseph Camin to aid learning about taxonomy & classification. Here’s what they look like (these are just the ‘living’ species):

The idea was to sort them – both ‘living’ and ‘fossil’ species – into groups on the basis of various similarities, & then to work out a possible family tree (a phylogeny) that reflected their possible evolutionary history. Camin used made-up ‘animals’ rather than actual organisms because he wanted to avoid students’ preconceptions about relationships affecting the development of their phylogenetic trees.

I must have found this rather fun because, when I was in the position of redeveloping a paper on the evolution & diversity of life, I remembered the Caminalcules & decided to use them as the basis of a lab class myself. As you do, I did a little googling & found not only the images of fond memory, but also a lab exercise developed by Rob Gendron, of Indiana University of Pennsylvania. Rather than reinvent the wheel, I e-mailed Rob & he very kindly allowed me to use his lab exercises in our BIOL201 paper. (And I’m extremely grateful that he was so generous with his resource – if you read this, Rob, thank you again!)

I must admit, I did wonder what today’s computer-savvy generation of students would think of a paper-&-scissors exercise, but apart from one or two who felt it a bit kindergarten-ish, everyone seemed to enjoy identifying the features that would (& wouldn’t) be useful in working out relationships & in building up what turns out to be quite a complex family tree. Along the way they learn about synapomorphies (features shared by a particular group that derive from a common ancestor for that group); how to recognise convergent evolution; and the taxonomic significance of vestigial characteristics (among other concepts). They’re also challenged to think about how environmental conditions might drive the diversity seen in some lineages of Caminalcules, and similarly, why other lineages appear to be in evolutionary stasis.

You can see that there’s a lot of concept development, & good hard thinking, going on in this lab. Because it’s such a good introduction to thinking about evolutionary history, I used it as the first lab in our 12-week semester, to give the students the framework into which to fit the concepts & ideas they’d be gaining as we worked through the rest of the paper. Camin’s original concept has turned out to be one useful, & long-lived, idea :-)


When I went looking for the image I’ve used here, I was enchanted to also find the “Snouters“, another family of imaginary creatures. (I actually have the book about them, thanks to one of my brothers.) So nice to be reminded that science doesn’t always match the popular image, but is also about creativity, imagination, & downright fun!

in the rush to ‘e-learning’, are we losing sight of our goals? Alison Campbell Feb 27


One of the ‘big things’ in schools these days seems to be the increasing expansion of e-learning. I’ve written previously on one school’s decisionto require all its new students to have iPads, or similar tablet-style computers. At the time I worried about whether, in the rush to embrace new technology, the question of whether its use would enhance student learning was being left behind. And a friend of mine who’s a secondary teacher recently said something similar: these technologies can be tools for learning but do not & should not replace the need for linking our teaching to a student-inquiry-based experiential and cognitive-conflict-based learning (which requires a lot of forethought & planning from teachers!).

That concern resurfaced yesterday as I was reading the NZ Herald‘ on-line edition (on my iPad, lol), & found one story citing a couple of US reports suggesting that perhaps e-learning isn’t all it’s cracked up to be.

The first of the Herald‘s references was to this report at Education News Colorado, which examines the performance of students who are taught entirely on-line (for a range of reasons, that could include having dropped out of “regular” schooling, living in an extremely isolated area, or for philosophical reasons. At this point I need to note that the news report is based on an analysis of on-line school data, & so far doesn’t appear to have been published in the science education literature. (However, the Colorado Department of Education annual report, from which the data are drawn, can be found here.) Nonetheless, the analysis does appear to highlight some rather worrying trends:

Online students are losing ground. Students who transfer to online programs from brick-and-mortar schools posted lower scores on annual state reading exams after entering their virtual classrooms.

Academic performance declined after students enrolled in online programs. Students who stayed in online programs long enough to take two years worth of state reading exams actually saw their test results decline over time.

Wide gaps persist. Double-digit gaps in achievement on state exams between online students and their peers in traditional schools persist in nearly every grade and subject — and they’re widest among more affluent students.

Now, one reason put forward by education officials for the apparently wide differences in results was that on-line education was pretty much an option of last resort, & certainly at least one Colorado virtual school does appear to target at-risk students who may well be behind on many educational indicators. However:

The analysis of state data shows, however, that most online school students do not appear to be at-risk students. Only about 120 students of the more than 10,000 entering online programs last year were identified as previous dropouts returning to school, and only 290 entered online schools after spending the prior year in an alternative school for troubled youth.

The obvious question is, why? Because there does appear to be something going on. And it’s relevant to NZ even though fully on-line teaching is a long way from the use of iPads & their like in a bricks-&-mortar classroom: we’re still looking at two stages on a continuum here.

Part of it could be that kids are not really as tech-savvy as we’d like to think. Putting them in front of a desktop computer, or giving access to things like tablets, doesn’t mean that they’ll necessarily use the technology to its best advantage. They may well need to learn that skill. And those using the technology to teach also need to think about how well it fits their learning objectives – is it there because it’s “there”, or because it enhances learning in some way?

Coming back to the full-blown exclusively on-line learning thing: there are also issues of community & pedagogy. In a real (as opposed to virtual) school, students are part of an actual community that includes both their peers & their teachers, & which can extend into the community outside of school. It can be rather isolating to be a distance student, & not be a part of that (this was certainly my experience when I was studying extramurally for my teaching qualification). And maybe that can have an effect on learning.

Which is where the pedagogy comes in. Certainly from a university perspective,we haven’t always been terribly successful at moving from the face-to-face to the on-line teaching environment. However, technologies like vide0-conferencing, skype, moodle & panopto can help to give some sense of belonging to a learning community – as can tailoring teaching materials to this alternative means of teaching & learning, instead of simply uploading everything in the format that’s used in ‘normal’ classes. Are some of the students in the Colorado study missing out on that sense of community?

And the Herald‘s second reference? It was to this story (from September 2011) in the New York Times, which carried out what looks like a fairly extensive investigation on the use of technology in schools, before concluding that

schools are spending billions on technology, even as they cut budgets and lay off teachers, with little proof that this approach is improving basic learning.

Now, that’s talking about the current status quo in parts of the US. New Zealand’s a long way back from what the NYT is describing, both in the extent of our technology roll-out & in the amount of money we have available for it. And the research into the effectiveness of on-line teaching & learning is certainly being done (here,here, and here, for example). (There’s also an interesting review of ‘virtual schools’ available here, which uses New Zealand as one of its examples.)

But still: technology, in education as elsewhere, is a useful tool, but not necessarily a panacea for all ills.

anti-vaccination anti-science Alison Campbell Feb 25


At Respectful Insolence, Orac has a recent post discussing ‘anti-science’, and I thought of this when I finally got around to writing this piece (which Grant has kindly ‘left to me’, as it were!). Here’s how Orac defines the term ‘anti-science’:

It’s an imperfect term for people who reject well-established science. To get a flavor of what being “anti-science” means, take a look at people who reject evolution, reject anthropogenic global warming, reject vaccines, and reject scientific medicine in favor of quackery.

Which is a reasonable characterisation of some of the content from the IAS website that Grant’s deconstructed, leaving this bit for me (because I asked nicely):

When a well meaning friend or relative questions your decision [not to vaccinate], simply say “I fail to see how injecting heavy metals, foreign proteins, multiple viruses and many toxic substances into a body all at one time can keep someone well, can you explain it to me?”

“Heavy metals”: could they mean (gasp!) mercury? It’s hard to tell, with such a non-specific term. But if they do mean mercury, then this phrase can only be construed as intending to mislead: mercury (as thiomersal) was phased out of New Zealand’s paediatric vaccines in 2000. In reality, the “heavy metals” actually include some elements that are required for life (such as iron, molybdenum, & cobalt) as well as the harmful ones like lead & plutonium – and mercury.

Dose & chemistry also matter. When childhood vaccines in NZ did have thiomersal in them, the mercury was in the form of the organic compound ethylmercury. Unlike methylmercury, ethylmercury has a half-life in the body of around 7-10 days: it is converted to an inorganic form & then excreted. As for dosage, back when our vaccines contained ethylmercury, a 6-month-old child who had received all recommended vaccines would have received a grand total of 175 micrograms of this substance, well below World Health Organisation guidelines.

‘Foreign proteins”? Which ‘foreign’ proteins are we discussing here? Presumably it’s the antigens included in vaccines to elicit an immune response. Which are no more, & no less, ‘foreign’ than the self-same proteins on the surface of a bacterium or the coat of a viral particle. In any case, it’s worth remembering that proteins & large polypeptides from food can cross the gut wall to circulate in the bloodstream, & they’re equally ‘foreign’.

“Multiple viruses”? It’s correct that some vaccines contain viruses. “Live” vaccines contain viruses that are attenuated but which stimulate an immune response in the host. Examples are measles, mumps, rubella, & chickenpox. “Inactivated” viral vaccines (eg for polio & influenza) have had their ability to replicate destroyed – this further reduces the extremely small risk of a “live” vaccine inducing disease, but requires much higher doses to elicit the same immune response. There are also vaccines based solely on viral protein subunits.

Let’s assume that the IAS’s “multiple viruses” refers to the MMR vaccine. Three viruses at once – sounds bad! However, viruses are extremely common in many indoor environments, so daily exposure to viral particles may be many orders of magnitude greater than the 3 in that particular vaccination. Many pathogenic viruses are airborne, entering the body through mucous membranes, and some can persist for up to several months on dry surfaces. Overall, an individual’s daily exposure to antigens is many orders of magnitude greater than exposure via vaccines.

As for the “many toxic substances” part (oh noes, teh ebil toxins!) – it’s notable that many of those who cite the presence of toxins appear quite unable to identify what they are. The term ‘toxins’ is presumably sufficiently scary to put hearers off asking for elucidation. At a guess, IAS might be referring to formalin, squalene, & or aluminium. However, once more dose is important. None of these are toxic at the concentrations found in vaccines – in the case of aluminium daily exposure through food & drink is far higher (hardly surprising when you consider that it’s one of the most abundant elements in the earth’s crust). And our bodies make both formalin (formaldehyde) & squalene as part of their normal metabolic functioning.

So, sad to say, that particular anti-vaccine website could fairly be characterised as anti-science.

here be dragons Alison Campbell Feb 21


This post is also on Talking Teaching.

Over on SciblogsNZ we had a bit of a discussion around the issue of science & belief systems. How far should scientists, & those who communicate about science, go in ‘pushing’ against strongly-held beliefs? (These could include creationism, but also beliefs about ‘alternative therapies’ such as homeopathy & TCM.)

It is an area where care is needed, because if you ‘push’ so hard that people feel their ideas are threatened, they may become defensive & those ideas more entrenched. Neither’s a desirable outcome from science’s point of view. On the other hand, in teaching about science, from time you actually need to put students in an ‘uncomfortable’ place regarding their conceptions about the world, if they’re to examine those questions critically & perhaps reshape them in the light of the new knowledge they’ve acquired. (If that doesn’t happen, then that new knowledge is likely to be learned only superficially – quickly gained & just as quickly forgotten.)

I’d like to reproduce a comment from that thread, partly because it would be good to get a discussion going around the question of how far & how best to promote a science-based world view, & partly because the comment reminded me of the late, great Carl Sagan: I’m just re-reading his 1995 book The Demon-Haunted World: Science as a Candle in the Dark. I enjoy the lyrical nature of much of Sagan’s writing, but I also like this book for it’s ‘baloney-detection tool kit’ – a set of useful questions & approaches to encourage & strengthen critical-thinking skills.

Anyway, here’s the comment:

[if we just accept a belief system], in the end we pass deeper into the land of moral equivalency (how dare you question my belief system – it’s as valid as yours!).

Here be dragons.

Dragons are best slain – no good comes from people attempting to turn them into pets, or ignoring the fact that they scorch the curtains and eat children.

What do you think about this?

have universities degraded to teaching ‘only’ scientific knowledge? Alison Campbell Feb 20

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The title for this post is taken from one of the search terms used by people visiting my ‘other’ blog (the one I share with Marcus & Fabiana), Talking Teaching. It caught my eye & I thought I’d use it as the basis of some musings (which are re-posted here).

We’ll assume that this question is directed at Science Faculties :-) Using ‘degraded’ suggests that a university education used to provide more than simply a knowledge base in science. (If I wanted to stir up a bit of controversy I could say – oh, OK, I will say – that it’s just as well that they ‘only’ teach scientific knowledge, however that’s defined. My personal opinion is that the teaching of pseudoscience (eg homeopathy, ‘terapeutic touch’ etc) has no place in a university, & it’s a matter of some concern that such material has appeared in various curricula eg in the US, UK & Australia. Why? Because it’s not evidence-based, & close investigation – in one case, by a 9-year-old schoolgirl – shows that it fails to meet the claims made for it. You could teach about it, in teaching critical thinking, but as a formal curriculum subjet? No way.)

Anyway, back to the chase. Did universities teach more than just ‘the facts’, in the past? And is it a Bad Thing if we don’t do that now?

I’ll answer the second question first, by saying that yes, I believe it is a Bad Thing if all universities teach is scientific knowledge – if by ‘knowledge’ we mean ‘facts’ & not also a way of thinking. For a number of reasons. Students aren’t just little sponges that we can fill up with facts & expect to recall such facts in a useful way. They come into our classes with a whole heap of prior learning experiences & a schema, or mental construct of the world, into which they slot the knowlege they’ve gained. Educators need to help students fit theri new learning into that schema, something that may well involve challenging the students’ worldviews from time to time. This means that we have to have some idea of what form those schemas take, before trying to add to them.

What’s more, there’s more to science than simply ‘facts’. There’s the whole area of what science actually is, how it works, what sets it apart from other ways of viewing the world. You can’t teach that by simply presenting facts (no matter how appealingly you do this). Students need practice in thinking like a scientist, ‘doing’ science, asking and answering questions in a scientific way. And in that sense, then I would have to say that I think universities may have ‘degraded’. Until very recently, it would probably be fair to say that the traditional way of presenting science to undergraduates, using lectures as a means of transmitting facts and cook-book labs as a means of reinforcing some of those facts (& teaching practical skills), conveyed very little of what science is actually all about. And it’s really encouraging to see papers in mainstream science journals that actively promote changing how university science teaching is done (here, here, & here, for example).

Of course, saying we’ve ‘degraded’ what we do does make the assumption that things were different in the ‘old days’. Maybe they were. After all, back in Darwin’s day (& much more recently, in the Oxbridge style of uni, anyway) teaching was done via small, intimate tutorials that built on individual reading assignments & must surely have talked about the hows and the whys, as well as the whats, of the topic du jour. However, when I was at university (last century – gosh, it makes me feel old to say that!) things had changed, and they’d been different for quite a while. Universities had lost that intimacy & the traditional lecture (lecturer ‘transmitting’ knowledge from up the front, & students scrabbling to write it all down) was seen as a cost-effective method of teaching the much larger classes that lecturers faced, particularly in first-year. In addition, the sheer volume of knowledge available to them had increased enormously, & with it, the pressure to get it all across. And when you’re under that pressure to teach everything that lecturers in subsequent courses what students to know before entering ‘their’ paper, transmission teaching must have looked like the way to go. Unfortunately, by going that route, we’ve generally lost track of the need to help students learn what it actually means to ‘do’ science.

Now, those big classes aren’t going to go away any time soon. The funding model for universities ensures that. (Although, there’s surely room to move towards more intimate teaching methods in, say, our smaller 3rd-year classes? And in fact I know lecturers who do just that.) But there are good arguments for encouraging the spread of new teaching methods that encourage thinking, interaction, & practicing a scientific mindset, even in large classes. Those papers I referred to show that it can be done, and done very successfully.

First up: there’s more to producing a scientifically-literate population than attempting to fill students full of facts (which they may well retain long enough to pass the end-of-term exam, & then forget). We need people with a scientific way of thinking about the many issues confronting them in today’s world. Of course, we also need a serious discussion at the curriculum level, about what constitutes ‘must-have’ knowledge’ and what can safely be omitted in favour of helping students gain those other skills. (This is something that’s just as important at the level of the senior secondary school curriculum!)

And secondly: giving students early practice at doing & thinking about science may encourage more of them to consider the option of graduate study, maybe going on to become scientists themselves. (In NZ graduate students are funded at a higher rate than undergraduates, and the PBRF system rewards us for graduate completions, so there’s a good incentive for considering change right there!)

I’m sure you can think of others :-)

choosing for the future Alison Campbell Feb 19


This one’s really intended for students in year 11/12, & their teachers & parents – those of my readers who are in year 13 will already have worked out where they’d like to be & made their subject choices.

In the weeks before the start of the A semester, my diary rapidly fills up with appointments as new and returning students come in for advice about their programs. For the latter group it’s usually fairly straightforward: have they met the various pre-reqs? Is their major remaining the same? How many papers do they need to complete their qualification? Things like that.

With new students, helping plan a program can be a bit more difficult, & often this difficulty also hinges on pre-requisites – the subjects (&/or the number of credits in a subject at Level 3 of the NCEA) that you need to have taken in order to study a particular subject at university. For example, for Engineering you need to have a certain number of credits in physics, maths (with calculus) and – for some areas – chemistry. The same’s true for Chemistry, Physics, & Maths. While my own subject – Biology – doesn’t have any formal pre-reqs, it’s still useful to have studied it at year 13 as we do tend to move along fairly quickly & you’ll probably feel more comfortable with that if you’ve got some prior learning in the subject. If someone comes along who’s never studied bio at all, I strongly encourage them to take a ‘catch-up’ course over summer. And while I remember – a bit of maths can never go amiss. Contrary to what many students seem to think, biology is not a maths-free zone & it’s useful to have some familiarity with basic maths concepts.

So for someone who doesn’t really meet the prior-learning requirements for a particular discipline but is set on studying it, we work with them to identify a pathway that will give them the best chance of succeeding with that goal. That ‘catch-up’ course is one avenue, after which we follow the tutors’ recommendations about what papers the student should be placed in. For someone with insufficient credits in maths or physics for  the papers specific to an Physics or Engineering program, we would enrol them in the relevant introductory papers (& on passing those, they’ll move to the degree-specific papers), plus encourage them to take up all available opportunities for extra tutorials & other learning support – & in fact I direct students from all disciplines to these resources as & when it seems necessary.

However, all of this imposes extra costs in terms of time & things like student loans, in that it will take a bit longer to complete the desired program of study. And one way to avoid this is to work with your teachers, careers advisers, & the recruitment staff from universities to identify where you want to be in terms of study & careers options and to do it early. Ask around – contact the universities you think you might want to attend to ask about pre-requisites for the degree programs you’re interested in, & then work with school to make sure you have the opportunity to achieve them.

(And yes, returning students can & do change their career intentions in ways that have a similar impact, in that they may have to take extra papers – & hence longer than originally intended – in order to achieve their goals. And again, the job of advisers like me is to work out the best options available for them to do that.)

on your bike Alison Campbell Feb 13


I drive a car. I also ride a bike to work a couple of days a week (an 18km round trip each time). And this is not a post on the science of either, but a plea to some car drivers for a bit more consideration (& road space).

Today I consider myself lucky to have got to work in one piece. To the driver of the white company van who came up fast on my right & turned left in front of me – yes, I know you indicated as you pulled alongside, but I still had to brake hard to avoid being collected as you shot down that side road. Were you really in such a hurry that waiting a couple of seconds for me to clear the intersection was going to cause an unbearable delay?

And the car driver who cut into the cycle lane ahead of me on that sweeping bend between 5 Crossroads & Southwell School – I wear a fluoro reflective jacket & have a cover of the same on my back-pack, there are reflective strips on my panniers, and my flashing lights were going front & back, so “I didn’t see you” would not have done you much good had you hit me with all the inevitable consequences of a heavy moving object hitting a much smaller one.

And don’t get me started on the idiots who think it’s a good idea to chuck bottles into the marked cycle-way, so that at rush hour cyclists have the choice of an almost inevitable puncture or to move onto the carriageway & take their chances with the cars.

Yes, there are cyclists who don’t obey the road rules & take foolish risks – just as there are car drivers who do the same. But most cyclists – like most motorists – are careful: we can imagine all too well the consequences if we aren’t. It would be wonderful if everyone thought about those consequences too – in an accident involving maybe 90kg of cyclist+bike travelling at 25kph, & a tonne or of car doing 50 (or even 25), the cyclist is always going to come off very much the worse for wear.

And I’d rather we all did our bit to avoid those consequences.


Actually, while I’m on my hobby horse erm, I mean ‘soapbox’ – could those cyclists who come rushing up at speed behind other cyclists (& behind walkers on the river paths) please please let those ahead know you’re coming? Ringing the bell would be good, or just calling out a cheery ‘excuse me’. It’s incredibly disconcerting to have someone whoosh past when you haven’t heard them coming (modern bikes really do run quietly). Thank you :-)

/vent over

these legs were made for walking… Alison Campbell Feb 13

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… but not in the middle of the night.

As I’ve got older, I’ve found that little bouts of nocturnal restlessness in the legs department have become more common. Apparently it’s called “restless legs” syndrome (RLS), which for me presesnts as a rather unpleasant, hard-to-resist feeling that you just have to move your legs, sometimes accompanied by having your legs jerking & twitching while you’re asleep. (Which then wakes me up, alas!). Trying to relax doesn’t seem to have any effect, & the whole thing can make it quite hard to drop off to sleep.

For a while I thought it was ‘just me’, but apparently up to 10% of the over-65 population (in Western countries, anyway) suffer from this syndrome, with women more susceptible than men. In fact, in a recent paper describing new work on identifying genetic markers for susceptibility to RLS. Winkelmann et al. (2011) identify it as “one of the most common neurological disorders.” As you might expect in a syndrome with neurological underpinnings, at least some of the genes implicated in RLS are involved in neuronal transcription pathways. However, it’s a complex issue as there may also be links with iron deficiency (there’s an interesting question: are people with iron-deficiency anaemia more likely to suffer from RLS than the general population?)

It’s even got a name: Willis-Ekbom disease. I really must check with my siblings as researchers estimate that about 60% of cases are familial ie there’s a genetic component: so far 6 gene loci are known to be linked to “restless legs”, with an autosomal dominant pattern of inheritance & variable ‘penetrance‘ (that is, the trait isn’t expressed in everyone carrying the mutation).

And what can one do about it? Well, I guess there’s always the pharmacological solution, if sleep disruption becomes a significant problem. But apparently you can also get relief by giving in to the urge to move your legs, so I’ll give it a go (trying not to kick the little black dog on the foot of the bed as I do so!).

Winkelmann J., Czamara D., Schormair B., Knauf F., Schulte EC, et al. (2011) Genome-Wide Association Study Identifies Novel Restless Legs Syndrome Susceptibility Loci on 2p14 and 16q12.1. PLoS Genetics 7(7): e1002171. doi: 10.1371/journal.pgen.1002171

arsenic & old crimes Alison Campbell Feb 12

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A commenter on one of Orac’s posts (& now I’m darned if I can remember which one) informed the others present that, while arsenic can be fatal for humans, it doesn’t kill rats. (It was part of a discussion on animal testing, which means the post was probably this one.) Now, I am a fan of the “Lord Peter Wimsey” books by Dorothy Sayers. One – Strong Poison – sees our hero attempting to clear a woman of using arsenic to murder her lover (a guilty verdict would have seen her sent to the gallows). It’s definitely not good stuff to consume in any quantity, although for a while arsenic in small amounts was regarded as a tonic in some circles.

But I also recalled that one source of the arsenic used for killing those whom the poisoner disliked, or wanted out of the way, was – rat poison. Another was fly-papers, which used to be hung to catch flies back when flyspray hadn’t been thought of. My recollection was confirmed when I came across this interesting post by Deborah Blum at Speakeasy Science, which discusses some notorious cases with arsenic as the murder weapon. (Deborah also muses on a question by another writer – why don’t we remember infamous personalities like Mary Ann Cotton, who killed at least 20 people, including some of her own children? She suggests, & I agree, that it’s a matter of choice “not to dwell [too long] in the darkest corners of human behaviour, to spend too much time in the company of aberrant personalities.”

Arsenic remained a common choice for poisoners until the advent of the Marsh test, at which point it became rather straightforward to detect the presence of arsenic in the deceased’s remains.

As for the rats – it takes around 763 mg/kg (or 0.763 g/kg) of arsenic to kill your average rat, although this particular poison is not part of the modern rat-killers armamentarium.

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