GENERAL SKETCH 



pipes, but after such passage the odor was extremely strong and 

 repulsive, while no colonies could be found. It was suggested at this 

 time that the odor was one of disintegratidn, and due to the libera- 

 tion of minute drops of oil-like substance which become disseminated 

 through the water, giving it the characteristic Uroglena smell. It was 

 also suggested that these drops of oil are analogous to the perfume 

 oils of the fragrant plants, like them having a certain individual odor 

 often strong enough and characteristic enough to identify the organ- 

 ism. Similar oil-like inclusions are found in the protoplasm of all 

 Protozoa, but to be detected through the sense of smell, they must be 

 present in great numbers. 



Far more serious noxious effects of the Protozoa are produced 

 through their frequently parasitic mode of life. In all classes there 



B 



D 



Fig. 31. Internal parasites. [A, B, LEUCKART; C, GRASSI ; D, BiJTSCHLl .] 

 A. Amaba colt Losch, a supposed cause of dysentery. D. Monocystis agilis Leuck., a grega- 

 rine. C. Megastoma. entericum Grassi, a flagellate. D, Balantidium entozoon Ehr., a ciliate. 



are certain forms which live as parasites (Fig. 31), and which for con- 

 venience may be separated into two groups, the intercellular and the 

 intracellular forms. So far as known these parasites, with few excep- 

 tions, do not produce noxious products like bacterial ptomaines, but 

 whatever damage they may cause is due to the mechanical disturb- 

 ances set up by their presence. The intercellular parasites infest the 

 body cavities of various hosts, the cavities of blood-vessels, and ducts 

 of various glands, or penetrate the spaces between muscle-fibres, while 

 the intracellular parasites (which belong almost exclusively to the 

 Sporozoa) bore into cells of epithelia (Gregarines, Coccidia), or the 

 corpuscles of the blood (Haemosporidiida). From the wide distribu- 

 tion of the intercellular parasites, it is quite possible that no animal is 

 entirely free from Protozoa of some kind. Without entering upon a 



