11« JOURNAL, B03IBAY NATURAL HISTORY SOCIETY, Vol. X. 



underlying muscles are reduced to an almost pulpy blood-stained substance 

 and post-mortem decomposition occurs very soojp after death. Similar changes 

 in the subcutaneous tissues, but to a rather less degree, are caused by the 

 diamantina venom, and in addition hsematuria, or more probably hsemoglobi- 

 nuria, was invariably produced by lethal and even by large non-lethal doses. 

 I mention these circumstances to indicate the perfection of the protection 

 vphich is produced by the administration of successive gardually-increasing 

 doses ; for they can be so adjusted that a dose of each venom, even three 

 times larger than the minimum lethal, may be administered without produc- 

 ing more than an inconsiderable and even scarcely observable degree of local 

 destructive effect. 



In the meantime, the process of protection with these latter venoms has 

 not advanced further than three times the minimum lethal dose. This, how- 

 ever, has been sufficient to allow experiments to be made by which it has been 

 demonstrated that when an animal has acquired a resistant power over the 

 minimum lethal dose of one venom, that animal is also able successfully to 

 resist the lethal action of a dose above the minimum lethal of other venoms. 

 To a rabbit immunised by cobra venom, a dose above the minimum lethal 

 of sepedon venom has been administered ; to rabbits immunised with crotalus 

 venom, doses above the minimum lethal of diamantina and of cobra venoms 

 have been given ; to animals immunised above the minimum lethal with the 

 diamantina venom, doses above the minimum lethal of crotalus and sepedon 

 venom have been given ; and in each case the animal has recovered, and but 

 few symptoms of injury were produced. At the same time, in other experi- 

 ments, indications were obtained that animals immunised with a given venom 

 are capable of resisting the toxic effect of that venom more effectually than 

 the toxic effects of other venoms. 



Duration of Immunity, 



My experiments have not yet proceeded sufficiently far to show for 

 what length of time the protection conferred by any final lethal dose may 

 last, I propose to make some experiments which will give definite informa- 

 tion in regard to this point, which may possibly lead to practical applica- 

 tions. It has incidentally been discovered, however, that protection lasts 

 for at least a considerable period of time, even when the last protective 

 dose has not been a large one. For example, to a rabbit which had last 

 received twice the minim un lethal dose of crotalus venom, the same dose 

 was administered twenty days subsequently, and it altogether failed to pro- 

 duce any toxic symptoms. 



As yet no sufficient data have been obtained for affording an explanation of 

 these remarkable facts. It is obvious that the blood of protected animals 

 must contain some substance or substances which are not present in the non- 

 protected animals, by which the lethal and toxic effects of venoms are pre- 



