268 



VENOMOUS ANIMALS 



Naja fiava, and N. nigricollis, N . tripudians, Echis carinata, with 

 perhaps the addition of Naja melanoleuca and Vipera russellii ; and 

 it is possible that further observations will show that all the Colu- 

 bridae and Viperidae have this power to a greater or lesser extent. 

 Of course the action is not spitting in the correct sense of the word, 

 but merely projection of venom, which causes conjunctivitis if it 

 enters the eyes, and a saltish taste if it enters the mouth. 



The HydrophidcB. — -Rogers experimented with Enhydrina vala- 

 kadienBoie, Distera cyanocincta Daud., ai.nd Hydrophis cantoris Gthr., 

 and came to the conclusion that their venom only differed from 

 that of the cobra in the following points:— 



1. They were more toxic. 



2. They were much less haemolytic, and hence caused no blood- 

 stained effusion at the site of the injecti:n. 



3. They did not affect the coagulability of the blood; therefore 

 the poison is almost purely neurotoxic. 



There is at first an excitation of the nervous system, leading to 

 a feeling of activity and vivacity, which, however, soon passes off. 

 The earliest signs of distress begin with difficulty of articulation 

 and feeling of stiffness in the body and of suffocation. The stiffness 

 in the muscles increases, and occasional spasms occur, while signs 

 of gastric irritation, with vomiting, appear. Convulsions and death 

 may ensue after a day or so. The local signs may be slight. 



Viperine Venom. — Vipera russellii Shaw, the tic polonga of 

 Ceylon, is a good example of this type of venom. Wall's experi- 

 ments show that a dog bitten by one of these vipers will become 

 convulsed, and die within five minutes. The cause of this sudden 

 death has been shown by Rogers to be intravascular clotting, which 

 is best marked in the portal vein, and then only in small animals. 

 Post mortem, there are haemorrhages into the area of the bite, and 

 into kidney and intestine. 



In addition to these acute cases, there are also chronic cases, in 

 which the local symptoms are more or less extensive subcutaneous 

 haemorrhages, around which there is much oedema. This haemor- 

 rhage may be absorbed, or the area may slough, or an abscess, or 

 even a spreading gangrene, may ensue. 



The general symptoms are rapid emaciation, profound anaemia 

 and lethargy, and in some cases haematuria and a discharge of blood 

 from the bowel. 



Rogers has carefully investigated these symptoms, and has 

 pointed out that there is a remarkable fall of blood-pressure due to 

 vaso-dilatation of the portal system, caused by action of the poison 

 on the central, and not the peripheral vasomotor apparatus, the 

 heart muscle being unaffected. Lamb and Hanna showed that in 

 chronic cases there is deficiency in the blood coagulability. 



In man there are the two small punctured wounds caused by the 

 fangs, around which the skin is swollen and livid and painful, The 

 swelling and discoloration spreads, and in the course of twenty-four 

 hours the patient becomes at first excited, with thready pulse and 



