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



to the antilytic action of normal blood serum. The negative results recorded by 

 Loeb and Fleisher {1910) may have been due to insufficient or faulty extraction of 

 the worm material, insufficient quantity of powder used in the experiments, or possibly 

 to the destruction of the hemolysin by drying at temperatures between 42° and 50° C. 

 The results recorded by Preti (iQoS) as regards the insolubility of the hemolysin in 

 salt solution and its resistance to boiling are at variance with those of other investi- 

 gators, and, as will be shown in the following pages, are not in harmony with the 

 results obtained by the present writer. Moreover, Preti 's results can not be accepted 

 as conclusive, owing to his failure properly to control his experiments. Alessandrini 's 

 attempt {1904) to associate the secretisn of hemolysin with the cervical glands of the 

 parasites is not sustained by Whipple {igog), who found the hemolysin in all parts 

 of the worm. 



It is interesting to observe that the different species of hookworms referred to in 

 the foregoing summary have the common biological property of secreting a substance 

 destructive to red blood cells. Inasmuch as hookworm disease is characterized by 

 severe anemia, the presence of a blood-destroying substance in the parasites is highly 

 significant. 



In addition to the hemolytic substance which is present in hookworms, Loeb and 

 his collaborators have shown that the hookworm parasitic in dogs {Ancylostoma 

 caninum) also secretes a substance which inhibits coagulation of blood in vitro (IvOeb 

 and Smith, 1904; Loeb and Smith, 1906; Loeb and Fleisher, 1910). The results of 

 experiments by these investigators with reference to the anticoagulins of hookworms 

 may be summarized as follows: In A. caninum a substance is present which retards 

 coagulation of blood in vitro. This substance which is present in the anterior part of 

 the worm and practically absent in the posterior part is not destroyed but is markedly 

 weakened by boiling for 15 minutes. The substance does not resemble hirudin, a 

 toxic constituent of the leech, but appears to resemble cobra venom so far as its physi- 

 ological properties are concerned. It is of interest to note in this connection that 

 Liefmann {1905), who rejects the view that the hookworm secretes a hemolysin, like- 

 wise rejects the view that this parasite secretes an anticoagulin, since he obtained 

 positive results in but one out of three experiments which he performed. Liefmann 

 ascribes his positive results to substances from the intestine which may have adhered 

 to the worms, namely, pancreatin and peptone. Loeb and Smith {1906) point out, 

 however, that in view of the fact that they washed the wonns carefully and that 

 neither peptone nor pancreatin is known to inhibit coagulation of dog's blood in 

 vitro, and further, in view of the fact that the posterior parts of the hookworms showed 

 but a slight anticoagulating effect on dog blood and that extracts of ascarids and tape- 

 worms from dogs did not retard the coagulation of dog blood, Liefmann 's contention 

 can not be sustained. 



The carefully controlled experiments of Loeb and his collaborators leave no room 

 for doubt as to the presence of a hemotoxin in A ncylosioma canimtm which inhibits the 

 coagulation of dog blood. Loeb and Smith ascribe etiological significance to this 

 toxin and believe that it has the power of causing small hemorrhages in regions of the 

 intestine that have been lacerated by the worms. 



The pathological role of the whipworm {Trichuris trichiura) parasitic in man is empha- 

 sized by Askanazy (1896), who states that this parasite feeds on blood, basing his 

 assertion on the presence of iron pigment in the intestine of the worm demonstrable 

 by the Berlin blue reaction. Askanazy assumed, of course, tliat the iron found in the 

 worm is obtained from the hemoglobin of the host's blood. Schultze (1905) rejects 

 Askanazy 's interpretation and considers tliat the pigment in question is obtained from 

 the host's intestine rather than from the blood. 



Guiart {1908) presents conclusive evidence as regards the bloodsucking habit of 

 Trichuris trichiura, since he found blood-engorged specimens in a human patient. 

 Guiart's observation has been confirmed by a number of investigators, including Garin, 



