Nov. 19, 1921 Hemotoxins from Parasitic Worms 389 



Owing to the fact that the direct abstraction of. blood by parasites 

 appears to be inadequate as an explanation of the causes of anemia in 

 parasitic diseases, and in view of the fact that in tapeworm infections 

 which are accompanied by anemia due entirely to the presence of the 

 parasites the direct abstraction theory is inapplicable, the view that 

 hemolysins from parasites are of etiological significance in parasitic 

 diseases appeared to be entirely justified. 



III. TECHNIC 



Unless otherwise indicated, the experiments described in the following 

 pages were performed with washed red blood cells. In most cases the 

 blood was defibrinated, filtered through gauze, centrifuged to remove the 

 serum, and washed in physiological salt solution at least three times to 

 free it from traces of serum. In a few cases a somewhat different pro- 

 cedure was followed. The blood was collected in a 2 per cent solution of 

 sodium citrate or in physiological salt solution containing i per cent 

 sodium citrate. The removal of the serum and subsequent washing in 

 physiological salt solution were carried out as in the case of defibrinated 

 blood. Unless otherwise stated, a 5 per cent suspension of corpuscles, 

 made by suspending i part of washed red blood corpuscles in 19 parts of 

 physiological salt solution, was used. 



Blood serum used in these experiments was obtained as follows: In 

 the case of rabbits blood was obtained by severing the marginal ear 

 vein, and in the case of the larger domestic animals it was obtained at an 

 abattoir from animals that were being bled and was allowed to drop 

 into a sterile centrifuge tube. The tube containing the blood was 

 allowed to remain at room temperature for a few hours. By means of 

 a sterile platinum wire the clot was loosened from the sides of the tube 

 to which it adhered and the tube was then centrifuged. The clear 

 serum was pipetted off, and if the serum was to be kept for more than 

 three days sufficient phenol was added to give a phenol content of 0.25 

 to 0.5 per cent; otherwise no preservative was added. 



Extracts of parasites were made from fresh material and from dried 

 material. In both cases the living specimens were obtained shortly after 

 they had been removed from the host. Certain writers who deny the 

 presence of toxic substances in parasitic worms base their objection to 

 the evidence in favor of the view that parasitic worms secrete toxic 

 substances on the grounds that extracts are frequently made from para- 

 sites that are obtained as a result of anthelmintic medication and that 

 the toxicity may be due to traces of anthelmintic which adhere to the 

 surface of the parasite or to secondary degeneration products of dead 

 worms. The present writer has been careful to use fresh specimens in 

 order to avoid complications of the sort just mentioned. It should also 

 be stated that the parasites obtained from the intestines and other organs 

 were washed in physiological salt solution and were transferred tliree or 



