296 JOURNAL, BOMBAY NATURAL IfLST. SOCIETY, Vol. XXI. 



the dose of venom sufficient to kill a rabit proved fatal to a mongoose in 

 twelve hours ; and, as the result of his experiments, concludes : — " The 

 mongoose is able to bear without discomfort very considerable doses 

 relative to its size, but its immunity is not absolute. If it generally 

 triumphs in its struggles with venomous snakes, it is chiefly due to the 

 extreme agility with which it is endowed." It is not quite clear whether 

 these experiments were made with the poison of the cobra or with that of 

 the West Indian "fer-de-lance" { Lachesis lanceolatus ) : apparently the 

 latter. 



Again Fleet-Surgeon G. W. Bassett-Smith writing in the " Encyclo- 

 predia Medica " in 1902 remarks : — " The mongoose is remarkably resistant 

 to cobra poison, requiring from 10 to 25 times as much venom per kilo, as 

 a rabit, to produce lethal eftects." 



It is obvious then that a mongoose's chance of life, once he is bitten while 

 greater than a rabbit's, yet depends on the quantity of venom injected, 

 being less than a fatal dose for him. It may be of interest to consider 

 whether the amount of poison injected by a bite from an average 

 cobra under normal conditions would be more or less than enough for a 

 mongoose. 



Now the minimum lethal doso of cobra poison for a rabit is, according to 

 the late Major Lamb, i.m.s., "OSS millegrammes per kilogramme of the 

 animal's weight. Taking the highest estimate of the dose for a mongoose, 

 25 times the above is 8' 75 millegrammes per kilo. If a mongoose weighs 2 

 kilos, which, I doubt, it follows that 20 millegrammes would be more than a 

 fatal dose. Now a medium-sized cobra will (again according to Lamb) 

 yield about 200 millegrammes of venom, while the fatal dose for an average 

 man is calculated at about 50 millegrammes. We have too good reason to 

 know that the latter dose and more is frequently injected, and it is 

 probable that a healthy cobra can, on occasion, inject the whole content of 

 its poison gland at a single eifort. It is, therefore, beyond question that 

 the danger, to a mongoose attacking a cobra, of receiving a fatal bite, if 

 fairly struck, is considerable. 



It appears then that the undoubted anti-toxic qualities existing in the 

 blood of the mongoose are not of themselves sufficient to secure more than 

 a very partial immunity. 



Bassett-Smith writes : — '"'Elliott believes that the success of this animal 

 in fighting cobras depends on (1) its great agility, (2) its habit of setting up 

 its fur, thus deluding the snake as to its vulnerable part. Its immunity is 

 due to the habit it has of seizing the snake by the head, and often by so 

 doing, incising the poison-gland with its sharp teeth, causing the venom to 

 escape and be swallowed by the mongoose ; this would also reduce the 

 possible amount to be injected down the fang. Then there is the inocula- 

 tion of minute quantities of venom from repeated but ineffectual scratch 



