BLACK WIDOW SPIDER — D'AMOUR ET AL. 



417 



experiments done upon rats in which the first bite resulted in severe 

 symptoms, a subsequent bite in less severe symptoms, and the third 

 in no symptoms whatever, from which he concludes that immuniza- 

 tion had occurred. As will be shown later, immunization develops 

 much more slowly than these results would lead one to believe. In 

 experiments done upon himself, Baerg obtained almost opposite re- 

 sults, the first bite causing only local pain, whereas the second was 

 followed by a very serious and painful chain of symptoms. 



We tested the question of the degree of exhaustion of venom in 

 biting by placing the spiders under conditions where one would expect 

 them to bite their hardest and to inject the maximum amount of 

 venom. These spiders are notoriously cannibalistic. It is a well- 

 known fact and one which we have observed repeatedly, that when 

 two mature females, especially if one is attending an egg sac, are 

 placed in one container, they will fight furiously until one or the other 

 has been bitten and killed. We placed spiders together under these 

 conditions ; in the first experiment the victor of one match was matched 

 with another victor; in the second, spiders were used which had only 

 bitten once. The results are shown in table 7. 



Table 7 



Table 8 



Mg 



Dry weight of glands from 20 spiders 4. 



Dry weight of debris 1. 48 



Dry weight of venom 2.52 



Dry weight of venom per spider 12S 



Dry weight per a. I. d .032 



The spiders in experiment 1 had bitten others twice within a half- 

 hour before being killed, those in experiment 2 had bitten others once 

 within a half-hour before being killed. These results show that the 

 glands still contain a considerable amount of venom — at least one- 

 fourth the total amount — even after the spider has used them twice 

 within the previous half-hour. It should also be stated that where 

 the spider was biting for the second time, the victim usually recovered. 

 No experiments were carried out to determine the length of time 

 necessary for regeneration of venom. 



Potency of venom in terms of weight. — The poison glands were re- 

 moved from 20 spiders and dried in air for 12 hours. They were 

 then weighed. Following thorough maceration in distilled water, 



