176 COLLECTED STUDIES IN IMMUNITY. 



METHOD OF OBTAINING THE POISON. 



The toad poison used in my experiments was derived from 

 bombinator igneus, the fire-toad, and from bufo cinereus, the common 

 garden toad. In order to obtain the poison, the skin of the abdomen 

 and back of a freshly captured toad was used, for the poison is present 

 in largest amounts in the skin. The muscles and blood serum of 

 the fire- toad also contain the poison, but in smaller quantities. 



After the toads were thoroughly rinsed with physiological salt 

 solution they were decapitated and skinned. The skin was again 

 rinsed with salt solution and then rubbed to a paste, as homogeneous 

 as possible, with powdered glass. After adding 2 to 3 cc. physiological 

 salt solution the mixture was filtered or centrifuged. The resulting 

 fluid had a feebly acid reaction, a greyish white color and a peculiar, 

 garlicky odor. Toluol was added as a preservative, and the fluid 

 'stored in the refrigerator. In the same manner I prepared an extract 

 from the skin of the garden toad. 



The extract of the skin of the fire-toad showed strong hsemolytic 

 properties; that of the garden toad the same, though only in traces. 

 (See Table III.) The following experiments refer only to the fire- 

 toad poison which, for short, we shall call "phrynolysin." The poison 

 of the garden toad was used merely for comparison. 



PROPERTIES OF PHRYNOLYSIN. 



Phrynolysin is an exceedingly labile body. Heating to 56 C., 

 exposure to light, the addition of alcohol, ether, chloroform, min- 

 eral acids, strong potash lye, pepsin and trypsin, all destroy it in a 

 short time. Drying the 'phrynolysin over anhydrous phosphoric acid 

 at room temperature weakens it materially. It does not dialyze. 



Since, as already mentioned, the extract from the toad skin pos- 

 sesses a faint acid reaction, requiring 1 to 1.3 cc. decinormal lye 

 for neutralization, it could be assumed that the acid reaction slowly 

 destroys the toxin. The destruction of the toxin, however, proceeds 

 in the same time in neutral as in feebly acid solution, so that the 

 acid reaction cannot possess any great influence. The hsemolytic 

 action is the same in acid as in neutral solution. 



The best preservative for this substance is toluol, first employed 

 by Ehrlich for preserving the toxins. Cold storage is also good. 

 After a time the fluid becomes cloudy, owing to the separation of 

 albumin, but it maintains its hffimolytic power unimpaired for A 



