484 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 64 



obtained. Crotalus venom, for instance, causes deleterious changes 

 in the tissues at the area of envenomation, changes in the red blood 

 cells, defects in coagulation, injury to the linings of vessels and to a 

 lesser extent damage to the heart muscle, kidneys, and lungs. While 

 most of the North American Crotalus venoms produce relatively minor 

 changes in transmission at the neuromuscular junction, the venoms 

 of the South American species produce marked changes in nerve con- 

 duction and neuromuscular transmission. When Crotalus venom is 

 injected intravenously there is an immediate precipitous fall in sys- 

 tematic arterial pressure with concomitant changes in venous and 

 cisternal pressures, heart rate, and respiration. These changes are 

 thought to be due principally to changes in the resistances of the pul- 

 monary circulatoiy parameters, and to some extent changes in the 

 cardiac cycle. 



EVIDENCE OF USE 



The black widow spider (fig. 2 and pi. 1, fig. 2) uses its venom to 

 paralyze or subdue its foe and to a lesser extent to assist in digestive 

 fmictions. The amount of the several enzymes in this venom is not 

 sufficient to have any serious eilect on man or most other mammals but 

 they certainly play a part in the breakdown of the tissues of the 

 spider's prey. In mammals, the venom induces a mild arterial hyper- 



FiGURE 2. — Black widow spider and egg sac in web. 



