62 THE VENOM OF HELODERMA. 



glands, were exposed every other day for 10 minutes. At the end of the treat- 

 ment we found that venom from these individuals, instead of having dimin- 

 ished in virulence, was somewhat more active than venom taken from other 

 animals which had not been exposed to the Roentgen ray, a fact that we attrib- 

 uted to the influence of the long period of rest enjoyed by the glands of the 

 Roentgenized helodermas. Six rats injected with the first venom taken from 

 these animals showed that its toxicity had undergone no change that could be 

 attributed to the Roentgen-ray treatment. 



EFFECTS OF VENOM UPON ANIMALS. 



When a warm-blooded animal receives a lethal dose of heloderma venom 

 the first conspicuous effect is a disturbance of respiration. The breathing 

 becomes quickened and the respirations are forced. After a time the respira- 

 tory rate diminishes and the respirations grow shallow ; finally they occur only 

 at long intervals, until after a period of respiratory spasm they cease alto- 

 gether. Meanwhile, other symptoms appear. The animal shows weakness 

 and falls down, and frequently, though not as a rule, has acute attacks of con- 

 vulsions. Reflex irritability becomes increased so that a slight sensory stim- 

 ulus is able to inaugurate an exaggerated response which resembles the re- 

 sponse obtained in an animal poisoned by strychnine. The hind legs hang as 

 if paralyzed and later the forelegs also appear paralyzed. If the skin of the 

 leg be pinched, however, a response is elicited, and this response may still be 

 obtained very shortly before the last respiration. The corneal reflex may be 

 obtained even later than the sensory skin-reflex. 



It was noted that when mice were injected subcutaneously with lethal 

 quantities of venom, one hind leg became completely paralyzed and spastic at 

 a time when complete paralysis was not present in the other hind leg. This 

 unilateral spastic and paralytic effect was not due to the venom being injected 

 into or near this leg, since the fluid was usually injected under the skin of the 

 thorax. Not only was the one leg spastic and paralyzed, but sensation was 

 almost completely lost in this leg. Pinching the skin or pricking with a pin 

 produced no response ; occasionally, however, pressure (pinching the entire leg) 

 would lead to a slight muscular response of the other leg. These symptoms 

 are general for all the mammals which we have used, viz, dog, cat, guinea-pig, 

 rabbit, rat, and mouse; but some of them appear more conspicuously in certain 

 species than in others. For instance, the apparent paralysis appeared most 

 marked in rats and mice and the strychnine-like response to stimulus was most 

 evident in guinea-pigs. The respiratory disturbances were substantially the 

 same in all animals, and it is to the interference with respiration that we must 

 attribute the immediate cause of death in the warm-blooded animal. 



Besides the abnormal symptoms common to all, certain species of animals 

 show other disturbances. In dogs and cats injection of venom causes vomit- 

 ing and discharge of urine and feces. It also causes a very copious flow of 

 saliva and of tears. In cats a noticeable symptom is loss of voice. The ani- 

 mal makes continuous crying movements, but without the production of 



