292 IMMUNO-CATALYSIS 



that antivenin neutralizes the clot-forming, proteolytic and necrotic 

 activities of venom. 



Discussing the relation of antitoxic, anti-thrombic and antiproteo- 

 lytic properties of a given immune serum he found that these three 

 properties do not appear simultaneously. Anti-thrombin appears first, 

 then anti-necrotin (antitoxin) and last anti-proteolytic antibody. Dur- 

 ing the first month of immunization there is a great difference between 

 the anti-thrombin and antitoxin. One ml, of serum of one of the 

 horses immunized for three months with the venom of C. terrificus 

 neutralizes in vitro the clot-forming activity of 0.7 mg. of this venom, 

 whereas it neutralized the toxin activity of only 0.15 mg. of venom. 

 The same anti-thrombin titer was maintained throughout this period 

 while the antitoxin property increased progressively, attaining the 

 power after six to seven months of neutralizing with 1 ml. from 0.5 

 to 0.7 mg. of venom. In the serum of animals immunized for a long 

 time with C. terrificus the relation between anti-thrombin and anti- 

 toxin is sufficiently constant and the titer of the former is an approxi- 

 mate indicator of the latter, which is in contrast to their relation at 

 the beginning of immunization. In the titration of antivenom sera the 

 neutralization of the neurotoxic effect of C. terrificus is the main 

 property. In the case of the venom of Lachesis the clot-forming action 

 plays the important role. Vellard found that the specificity of anti- 

 venom sera does not obey a general rule. The study of various samples 

 of antivenins showed that some of them exercise more anti-thrombin, 

 and the other more anti-neurotoxic activity.* 



In a similar study on the enzymic activities of snake venoms 

 Githens (1941; also Githens and Wolff, 1939) made the following 

 observations. The venoms of crotalidic snakes injected subcutane- 

 ously or intradermally induced a local reaction characterized by 

 necrosis of tissue, hyperemia and edema, the last being seen especially 

 with subcutaneous injections. The reaction was studied on guinea 

 pigs injected subcutaneously over the hip, or intradermally on the 

 flank. A 1:1000 solution of venom was found most suitable for this 

 study; more dilute solutions engendered a more extensive edema but 

 with less necrosis. The skin near the site of injection soon showed a 

 yellowish, or more commonly a reddish-brown discoloration, which 

 reached its maximal extent in about two days, and was surrounded by 



*For a review on animal venoms, see Essex (1945). 



