116 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XV. 



Other creatures are slightly immune, as pigs and guinea-fowl ; the latter, 

 according to Calmette, being to a slight degree protected by having large air 

 sacs. It has lately been shown by Calmette and others that the resisting 

 power to venom becomes greater the larger the animal ; thus it takes a 

 much smaller dose of venom proportionally, volume for volume, to kill a 

 vabbit than a dog, man being even more resisting. 



Venom is obtained pure from the different poisonous snakes by either 

 making them discharge the fluid direct into a watch-glass, this being assisted 

 out by gentle pressure applied to the poison glands, the snake being held 

 in the hand with its head directed away from the operator as described by 

 Calmette ; or the venom may bd obtained by causing the snake to bite at a 

 wafch-glass covered with gutta-percha, the fluid collecting on the under side. 

 The venom should be taken from a fasting snake esrery two weeks or so. 

 From a good-sized cobra about 2-3 c.cm. is the average quantity obtained by 

 Calmette, after which he generally artificially feeds the snake. 



The venom thus collected has much the same appearance in all snakes — 

 a limpid fluid of yellowish colour ; from the cobra it is a faint yellow, that 

 of the hamadryad being a golden yellow ; it has a slightly acid reaction and 

 an average specific gravity of 10'50 ; a bitter taste is said to be present in 

 the venom of the cobra, but not in that of the Daboia. When the venom is 

 placed under the microscope, nothing should be seen except a few epithelial 

 cells and perhaps some contaminating bacteria. When kept moist, it gra- 

 dually becomes more acid and decomposes, forming a coagulum, the fluid 

 remaining poisonous. 



Venom, when dried at a moderate temperature, 20° C., forms reddish- 

 yellow or brownish-yellow crystalline scales, or it becomes agglutinated into 

 little masses like gum-arabic. When thus dried and kept in the dark, it 

 retains its toxic powers indefinitely. The dried residue equals in weight 

 about 20-30 per cent, that of the moist venom. If the venom be heated at 

 once after collecting to a temperature of 100° C., its toxic effect becomes 

 impaired, and also if it be exposed to light. 



The poisonous properties of all venoms depend upon the presence of at 

 least two distinct toxic proteids. These protrids are similar to other albu- 

 moses produced fiom albumens, which may have been obtained by 



(1) Boiling under high pressure. 



(2) Gastric and pancreatic digestion through the agency of a ferment. 



(3) The direct vital activity of cells. 



(4) By certain micro-organisms, as Bacillus diphtherix, B. tuberculosis, and 

 B. anthracis ; by means of a ferment in the case of diphtheria, but by the 

 direct action of the other two. 



The proteids of venom are elaborated by a process of dehydration of albu- 

 men, without the action of any ferment by the epithelial cells of the poison 

 glands, the ultimate product stopping short at the albumenose stage, not 

 proceeding to the production of peptones as occurs in all the before-men- 



