420 Journal of Agricultural Research voi. xxii. No. s 



To one tube a small quantity of carbolized^ horse blood serum was 

 added. The serum inhibited hemolysis. 



Haemonchus contortus powder was also tested on four samples of 

 washed cattle blood cells. The results were slightly positive after 2 

 hours at 37° C. followed by 18 hours in a refrigerator. 



Inasmuch as in the experiment described above washed red blood 

 cells were used, a series of tests were performed in which unwashed 

 defibrinated blood was used. In this series six samples of cattle blood 

 were involved. The addition of various quantities of Haemonchus 

 contortus powder yielded negative results after 3 hours at 37° C. 



Summarizing, salt-solution extracts of Haemonchus contortus are very 

 slightly hemolytic to sheep and cattle erythrocytes. The faint hemo- 

 lytic property is preserved by drying. The weakly positive results 

 obtained by experiments in vitro do not favor very strongly the view 

 which has been commonly accepted as regards the secretion of a hemo- 

 toxin by H. contortus. It is quite possible, however, that the appar- 

 ently weak hemolysin requires some activator which is supplied by the 

 host blood. The fact that experiments in vitro were only slightly 

 positive by no means precludes the possibility that an absorption by 

 the host of the secretions of H. contortus is followed by a marked hemo- 

 lysis. Another possibility, which has already been mentioned, is that 

 only the blood of young animals is susceptible to the secretions of H. 

 contortus. The subject requires further investigation. 



XI. EXPERIMENTS WITH TRICHURIS DEPRESSIUSCULA EXTRACT 



A small series of experiments with an extract of Trichuris depressi- 

 uscula was performed as follows: About 60 specimens collected from 

 several dogs were thoroughly washed in physiological salt solution and 

 dried in an incubator. The dried specimens were then triturated and 

 extracted in 3 cc. of salt solution overnight at 8° C. The clear filtrate 

 was tested on rabbit and sheep erythrocytes. Five drops of a 5 per 

 cent suspension of rabbit blood cells were hemolyzed by 3 drops of 

 extract in about 2 hours at 37°. Equal mixtures of sheep erythroc}'tes 

 and extract showed no hemolysis. The extract was boiled for about a 

 minute, and after it had cooled it was tested on rabbit erythrocytes. 

 It produced a faint indication of hemolysis, showing that boiling prac- 

 tically destroyed the hemolysin. 



XII. EXPERIMENTS WITH CESTODE HEMOLYSINS 



It has already been stated that while an active hemolytic agent has 

 been shown to occur in Diphyllohothrium latum, evidence that other 

 species of tapeworms secrete hemolytic substances is rather incomplete. 

 The presence of a hemolytic agent in D. latum is significant in view of the 

 fact that this parasite is capable of producing a severe anemia under 



' 0.25 per cent solution of carbolic acid in senun. 



