32 METHODS OF EXAMINING FECES FOR PARASITISM. 



LIMITED APPLICATION OR INCOMMENSURATE RESULTS. 



In regard to the second point, experience shows that in using 

 specific gravity as an aid in concentration it is safe to assume that the 

 specific gravity of a parasite is greater than water, though all eggs 

 will not go to the bottom, as some are held up by lighter material, 

 bubbles, etc., but it is not safe to rely on a parasite floating on a solu- 

 tion of specific gravity greater than itself for any length of time, 

 owing to the action of endosmosis. An additional objection to this 

 method advocated by Bass (1909) is that experience shows that all 

 the steps are not warranted by the results. In most cases the simpler 

 methods used by the writer give as good or better results. The use of 

 the 1.050 solution appears to be a defect of the method. The concen- 

 tration attained by it seems trifling in any case and at times it 

 apparently results in actual loss of parasite material. Finally, under 

 the same class of objections, experience shows that the concentra- 

 tion obtained by the use of chemicals instead of water (Telemann, 

 1908) is no greater than that obtained by the use of water alone, and 

 hence there appears to be no reason for using the more expensive 

 chemicals, especially in view of the injury to the microscope which 

 one of them occasions. It might also be urged that the odor of these 

 chemicals is such that one would prefer to avoid them, though it is 

 also true that they deodorize the feces after a fashion, and that while 

 they kill the parasites they also disinfect the feces in cases where the 

 killing is immaterial. 



DISINFECTION OF FECES. 



Disinfection and deodorization of feces can be more easily accom- 

 plished, if desired, by the use of formol solution instead of water, as 

 suggested by Letulle (1905). Jones (1907), and Garrison (1910). In 

 a discussion of this point before the Helminthological Society of 

 Washington, December 1, 1910, Dr. Stiles advocated the use of coal- 

 tar disinfectants on the ground that protracted work with formol 

 material would cause headaches. The writer has never experienced 

 any inconvenience from the use of formol. Dr. Stiles also pointed out 

 the great desirability of using some disinfectant, for the reason that 

 the greater number of fecal examinations now being made in this 

 country are for evidence of hookworm infection, and the localities 

 with the greatest amount of hookworm infection have a high typhoid 

 index. In using a disinfectant, the waiter's method of comminution 

 has the advantage of bringing the disinfectant into intimate contact 

 with all parts of the fecal mass. The thorough breaking up of the 

 feces and the use of large amounts of water reduces the, odor to a 

 point where it is almost imperceptible in most cases. 



