168 COLLECTED STUDIES IN IMMUNITY. 



causes of this poisonous action. Such a study, moreover, is calcu- 

 lated to extend our knowledge of the receptors and their physio- 

 logical distribution in the animal kingdom. While examining an 

 extract derived from the common garden spider (Epeira diadema) 

 I found in it a hsemolysin which showed itself particularly well 

 adapted to researches in this direction. 



The description of a complete experiment will give an idea of 

 the method of obtaining and testing this poison. 



A garden spider weighing 1.4 grams is rubbed up with 5 cc. toluol water 

 containing 10% NaCl and the fluid kept in the refrigerator for twenty-four 

 hours. Then water is added to make the total volume 25 cc. and the mixture 

 filtered (or centrifuged). The haemolytic experiments are made in the usual 

 manner with this cloudy, brownish-yellow filtrate. Decreasing amounts of 

 the poison solution are placed in a series of test-tubes, each of which is then 

 filled up to 1.0 cc. with physiological (0.85%) salt solution. Each tube now 

 receives one drop of undiluted blood or 1 cc. of a 5% suspension of blood in 

 physiological salt solution. The specimens are kept in the incubator at 37 C. 

 for two hours, and then in the refrigerator until the following day when the 

 amount of solution is determined. The blood employed was always centrifuged 

 and washed in order to remove the adherent serum and so exclude any possible 

 disturbance from that source. 



The Arachnolysin, as we may designate the active principle of 

 the poison solution, causes solution of the sensitive blood-cells even 

 at room temperature; when present in certain proportions, solu- 

 tion occurs almost instantaneously. In this respect, arachnolysin is 

 somewhat analogous to snake venom, while it differs therein from 

 the hffimolysins of blood serum, in which, as is well known, actual 

 haemolysis is preceded by a longer or shorter period of incubation. 

 The more exact determinations on different species of blood were 

 made in the usual manner and yielded the results shown in the fol- 

 lowing table. The amounts of arachnolysin given in the table refer 

 to the original solution, containing 28% of spider substance. 



As can be seen from the table we are here dealing with a hccmolysin 

 of extraordinary power, the action of which on the individual species 

 of blood, however, is very variable. Thus a number of species of blood 

 are destroyed even in dilution of 1 : 1000 or 1 : 10000 (this refers to 

 the original poison solution) ; others remain unaffected even by large 

 amounts of poison. Next to rat blood, the most sensitive was 

 rabbit blood, for 0.0001 cc. of the original solution, i.e., 0.000028 g. 

 spider substance, sufficed to completely dissolve 0.05 cc. blood 

 (=200,000,000 blood-cells). A garden spider weighing 1.4 g. there- 



