Poisoning Pigeons in the Park... Strychnine and Cyanide

Irish Baritone, Ben Russell, was our guest artist for this year's Phyllis Dence Performing Arts Day. Amongst other things Ben gave us a wonderful version of the old Tom Lehrer classic "Poisoning Pigeons in the Park"

Ben sang of using strychnine and cyanide to poison his pigeons, and this got us thinking about how such poisons work...


Strychnine is a naturally occurring, colourless, bitter, crystalline alkaloid compound of carbon, hydrogen, nitrogen and oxygen C₂₁H₂₂N₂O₂. When inhaled, swallowed or absorbed through eyes or mouth, it interferes with the action of motor neurone inhibitors, resulting in 'over stimulation' of motor neurones - causing muscular convulsions and eventually death through asphyxia. As it produces some of the most dramatic and painful symptoms of any known toxic reaction strychnine poisoning is often used in literature and film.


Strychnine is produced by plants of the genus Strychnos which are trees and climbing shrubs found in warm regions of Asia, Africa and America. The seeds and bark of many species are highly toxic, and seeds of Strychnos nux-vomica, from Indonesia, have long been used as a source of rat poison.




Cyanide is any compound containing a carbon atom triple-bonded to a nitrogen atom (a 'cyano group'). Hydrogen cyanide, in the form of Zyklon B, was used by the Nazis in World War II gas chambers and cyanide crystals (potassium cyanide or sodium cyanide) occur frequently in the world of 'whodunnits' such as in Agatha Christie's Sparkling Cyanide.


Cyanide inhibits the action of an enzyme (cytochrome c oxidase) which is needed for cellular respiration. When active in a cell's mitochondria the supply of energy (in the form of ATP) is interrupted and the cell stops working and ultimately 'dies'. Tissues that depend highly on aerobic respiration, such as the central nervous system and the heart, are particularly affected.


Cyanides are produced by certain bacteria, fungi, and algae and are found in a number of plants e.g. the 'stones' of apricots and pips of apples. The cyanide helps to protect plants against herbivores, although the golden bamboo lemur of Madagascar is immune to the high levels of cyanide in the Madagascar bamboo.


Oh by the way, It's 'Science Week ' this week and all of Stover is involved in uncovering who poisoned our science technician - based on various experiments and analyses being carried out in this week's Science lessons!

Mammals of the British Isles - The Squirrel

Grey Squirrel

Strangely enough, the cute and lovable grey squirrels (Sciurus carolinensis) we see playing in the grounds of Stover School are in fact rodents – the same group of mammals as rats. Since their introduction from North America, they have had a catastrophic effect on the native red squirrel (Sciurus vulgaris) throughout the British Isles. Grey squirrels also cause significant damage to woodlands through ‘bark stripping’ and reduce density and diversity in populations of woodland birds.

Wild grey squirrels first appeared in Britain in the late 19th Century, with some possibly escaping from London Zoo. In Italy two pairs escaped from an ambassador's garden in Turin in 1948, although some sources suggest that pet grey squirrels had already escaped in Piedmont by the late 1800s. The spread of grey squirrels, at the expense of native red squirrels, appears to have had a more marked effect in the British Isles than on mainland Europe – so far at least.

Red Squirrel

There are now thought to be just 140,000 red squirrels in Britain, whilst there are over 2.5 million greys, and the future of the red squirrel is becoming increasingly uncertain as they are now extinct in southern England (except for a few on the Isle of Wight). Red Squirrels are still widespread in the North of England and Scotland, but even here their range is contracting. The grey squirrel is having such a profound impact on British wildlife that the International Union for the Conservation of Nature has now listed it on their global list of the 100 worst invasive species. The UK Forestry Commission is working with partners in projects across Britain to develop a long-term conservation strategy that deters greys and encourages reds.

The Grey Squirrel is larger and more aggressive than its European cousin, and greys out-compete reds for food, feeding more on the ground and being able to digest acorns, which reds can’t. Contrary to popular opinion, red squirrels do not hibernate – but as greys can build up and store more fat they are better at surviving cold winters. Grey squirrels are also more generalist feeders eating: nuts, flowers, fruits, seeds, tree bark, fungi, bird eggs, nestlings and frogs - whilst reds prefer the seeds of coniferous forests, although they will diversify under pressure. Grey squirrels are also thought to have introduced the squirrelpox virus from North America which is deadly to red squirrels, although greys have a natural immunity.

Distribution of Grey Squirrel

Distribution of Red Squirrel

Grey squirrels, which can live at high population densities in broadleaved woodland, cause significant damage to trees such as sycamore, beech, oak, sweet chestnut, pine, Norway spruce and larch, by bark-stripping. This dramatically reduces the economic value of woodland – costing more than £10 million per year. They may also be partly responsible for recent declines in many woodland bird species - through predation of eggs and young chicks, competing for nest sites or because they consume food which would otherwise be available for birds.

Squirrels build large nests, called dreys, often in the forks of tree trunks. They can breed twice in a season, in spring and in late summer, but usually only breed once. There are between one and six young in a litter. The young are born naked and blind. Young squirrels may stay with their mother until she has her next litter. Mortality is quite high, with only one in five surviving to their first winter. Adult squirrels have few natural predators, as they are far too quick and agile for most.

this article is based on work by Jane Chen, Year 10

Year 11 Pupils Investigate the Kidney

As part of their GCSE Biology course, Year 11 pupils today investigated the structure of the kidney.

The Dissection Begins

The kidneys are two bean-shaped organs attached to the rear wall of the abdominal cavity. They have a rich blood supply, and as the blood passes through them it is filtered by millions of little structures called nephrons, consisting of: a glomerulus (a coiled ball of capillary blood vessels), and a kidney tubule (of which there are over 1 million, or 60 km worth per kidney).

A Nephron

Finishing Touches

Blood flows into each glomerulus from the renal artery. Small molecules ‘leak out’ under pressure filtration, into the Bowman’s capsule of the tubule. The small molecules are: water, urea, sugar and salt. The urea and most of the water flow down the tubule to a collecting duct and ultimately into the ureter and bladder to be excreted as urine. Useful materials however, like glucose and salt, are actively transported back into the capillaries surrounding each tubule – a process known as selective reabsorption.  

In cross-section, a kidney has two main regions: the outer cortex is lighter coloured, and contains the glomeruli and the beginning and end of each nephron. The inner medulla contains the middle u-shaped part of each nephron (e.g. the loop of Henlé). The medulla extends into the central ‘pelvis’ of the kidney as projections called pyramids.

Kidney in Cross-Section

Kidney Structure

Further Research