158 Canadian Record of Science. 



Parasitic Protozoa. 



W. E. Debks, B.A., M.D, 



It is not the purpose of the writer to bring forward any 

 new data in regard to the organisms considered, but merely 

 to give a somewhat popular summary of three types of Pro- 

 tozoa which are capable of entailing grave disturbances in 

 man when they gain access to his tissues. The various 

 branches of science have multiplied so rapidly in recent 

 years and the results achieved by the small army of inves- 

 tigators are so numerous, that it is very difficult to keep 

 pace even in one department. 



When the morbid processes present in man began to 

 be studied microscopically for their aetiological factors, it 

 was scarcely anticipated that living organisms were the 

 prime cause in a great many instances. Such, however, is 

 the case, and in consequence pathologists unintentionally 

 became biologists. The fact that the majority of the 

 results published by the former class of men are to be 

 found only in Medical and Pathological journals, and the 

 thought that probably a summary of some of the results 

 connected with certain forms of Protozoa and their relation 

 to disease might not be uninteresting to the readers of the 

 Eecord, have prompted this paper. 



For a long time it has been known that the alimentary 

 tract of different animals is subject to the presence of para- 

 sites, some of the stages of which may penetrate the deeper 

 tissue and there remain until death, in an encysted con- 

 dition, or in some cases may even cause death by their de- 

 predations as in Trichinosis. Familiar examples of these 

 are the Nematoda or round worms of a great many dif- 

 ferent speeies; the Trematoda or flukes, which pass some of 

 their stages in the intestinal canal and livers of the host 

 causing the fatal condition in sheep known as the liver rot; 

 and the Oestoda or tape worms, which require to pass 

 through two hosts generally before the different phases of 

 its life cycle are completed. The no less familiar instances 

 of the different members of GEstridai whose larva? are found 

 in the stomach as the botfly, or beneath the epidermal tis- 



