LIFE-TESTS. 
45 
§34-] 
1 to 30,000, causes most marked symptoms. The first sign is relaxation 
of the chromatophore muscle and the closing of the chromatophores ; 
the animal pales, the respiratory movements become more powerful, 
and at the end of a notable augmentation in their number, they fall 
rapidly from the normal number of 25 to 5 a minute. Then tetanus 
commences after a time, varying with the dose of the poison ; the arm 
stiffens and extends in fan-like form, the entire body is convulsed, the 
respiration is in jerks, the animal empties its pouch, and at the end of 
a few minutes is dead, in a state of great muscular rigidity. If at this 
moment it is opened, the venous heart is found still beating. Nicotine 
and other poisons were experimented with, and the cephalopoda were 
found to be generally sensitive to the active alkaloids, and to exhibit 
more or less marked symptoms. 
4. Insects. —The symptoms which may be distinguished in poisoned 
flies are dullness or vivacity of movement, loss of power of progression, 
paralysis of legs or wings or both, protrusion of the fleshy proboscis, 
disorderly movements, and so forth. 
Flies are caught without injury by swiftly placing over them a 
watch-glass on the window-pane ; a card is then inserted under the watch- 
glass and the fly or flies transferred to a table in a good light. Powders, 
extracts, liquids can now be easily introduced into the watch-glass, or 
the first watch-glass may be placed on another ; in either case, owing to 
the confined space, the insect becomes soiled with the substances placed 
under the watch-glass, and also usually sucks some up in the efforts to 
cleanse itself. 
As controls may be used a fly untreated and one submitted to a 
little of the powder of the Pyrethrum rosea, one of the most powerful of 
the insecticides. 
In the presence of pyrethrum powder, within four minutes there is 
much excitement; in from two to three minutes longer, disordered move¬ 
ments, loss of balancing power, paralysis of the wings occur, and the fly 
generally lies on its back, death taking place in from two to three hours. 
In poisoning by sausages, bad meat, curarine, and in obscure cases 
generally, in the present state of science, experiments on living animals 
are absolutely necessary. In this, and in this way only, in very many 
instances, can the expert prove the presence of zymotic, or show the 
absence of chemical poison. 
The Vivisection Act, however, effectually precludes the use of life- 
tests in England save in licensed institutions. Hence the “ methods ” of 
applying life-tests described in former editions will be omitted. 
§ 34. Effect of Poisons on the Heart of Cold-blooded Animals. —The Vivisection 
Act does not, however, interfere with the use of certain living tests, such, for instance, 
as the testing of the action of poisons upon tho recently extirpated hearts of cold¬ 
blooded animals. 
