414 Journal of Agricultural Research voi. xxn. no. s 



of fresh worms and placed on ice for 3^^ hours. The mixture was 

 centrifuged and the supernatant fluid was removed and to it there were 

 added 2 drops of washed dog corpuscles from the same lot as used in the 

 first part of the experiment. After 1 hour's incubation followed by 18 

 hours in a refrigerator the corpuscles remained intact. The corpuscles 

 from which the supernatant fluid was originally removed were washed 

 three times in salt solution and then incubated with a small quantity of 

 salt solution for i hour. Complete hemolysis was produced. A control 

 tube containing a similar quantity of corpuscles without any hemolytic 

 extract showed no hemolysis when placed in an incubator. While this 

 experiment appears to indicate that the hemolysin was fixed to corpuscles 

 and was not removed by repeated washing, this conclusion must be 

 accepted with caution, because the possibility remains that some frag- 

 ments of worms which were introduced into the tube together with the 

 hemolysin may have been responsible for the hemolysis of the corpuscles 

 after the removal of the supernatant fluid. The fact that the latter had 

 lost its hemolytic power affords, however, strong presumptive evidence 

 of an absorption of the hemolysin by the blood corpuscles. 



6. DISCUSSION 



The results of experiments with reference to the presence of a soluble 

 hemolysin in hookworms (Necator and Ancylostoma) show quite con- 

 clusively that when living specimens are macerated in physiological 

 salt solution they yield a considerable quantity of hemolysin. The latter 

 is characterized by relative thermolability, nonspecificity, and suscepti- 

 bility to normal serum, in the presence of which it loses its potency. 

 So far as its physiological properties are concerned, hookworm hemolysin 

 resembles strep tocol5^sin, staphylolysin, tetanolysin, and other hemoly- 

 sins of bacterial origin. It differs from the hemolytic substances of 

 Diphyllohothrium latum in that it is destroyed by boiling. The con- 

 clusion of Preti {igo8) that hookworm hemolysin is resistant to boiling 

 is not sustained by Whipple {1909) and is also contradicted by the 

 results of the present writer's experiments. Unfortunately, Preti has 

 not published a full account of his experiments. His general conclusions 

 are unsupported by details, and judging from the statements that he 

 makes it does not appear that he controlled his experiments. 



The present writer's experiments indicate that the hookworm hemolysin 

 is rather firmly bound to the tissues of the parasites, which probably 

 accounts for the difficulty of obtaining strong hemolytic filtrates from 

 salt solution extracts of powdered specimens. That the living worm 

 secretes the hemolysin is evident, however, from experiments with ex- 

 tracts of fresh worms. The unbound hemolysin from fresh specimens 

 evidently disappears in the course of drying. This comparative insolu- 

 bility of the hemolytic substance from dried specimens in physiological 

 salt solution is perhaps the basis of the contention of Preti {1908) and of 



