414 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 8 



Table 2 



Batch 



Number of 

 rats in- 

 jected 



Amount injected 



Percent 

 dead 



l 

 1 



2. 

 2. 



Equivalent of 2 spiders 

 Equivalent of 1 spider. 

 Equivalent of 2 spiders 

 Equivalent of 1 spider. 



TOXICITY CURVE- -VENOM 

 10 RATS PER DOSE 



1005? 



In view of the inconsistent results shown above we adopted the 

 following procedure as a routine method in the preparation of all 

 venom used in the succeeding experiments. No fewer than 20 spiders, 

 in some cases as many as 80 spiders, were used in the preparation of 

 each batch of material, and in this way individual differences were 



averaged. The spiders were 

 placed under light chloro- 

 form anesthesia, the abdo- 

 men clipped off and the 

 cephalothorax and legs im- 

 bedded in molten paraffin 

 on a microscope slide. 

 Solidification of the paraffin 

 held the spider in a firm 

 mounting. Under the dis- 

 secting microscope the skin 

 of the head above the eyes 

 was clipped off; the venom 

 glands were then clearly 

 visible and could be re- 

 moved with fine forceps. 

 The glands were then 

 placed in physiological salt 

 solution and carefully pulled 

 apart and thoroughly macerated. The glandular debris was trans- 

 ferred to fresh saline, again macerated and washed and discarded. 

 The washings were added to the original solution. 



Young rats, 50 to 60 grams in weight, were chosen as test animals, 

 first, because of their availability in this laboratory; and second, 

 because preliminary experiments showed that they were quite suscep- 

 tible. A relatively small amount of venom would cause death and 

 an adequate amount would produce a chain of symptoms which was 

 a very definite and constant one. 



The toxicity curve. — The work of Trevan (1927) on biologic assays 

 in general and the work of Coward and Burn (1927) and ourselves 

 (1930) on the assay of estrin preparations has clearly indicated the 

 necessity of using large numbers of animals in the assay of biologic 



Spider \ 

 Equivalents/ 

 m.g dryl 

 venom J 



1/8 1/4 



.016 .032 



Figure 1. 



.064 



.096 



