364 CLINICAL BACTERIOLOGY. 



IL INFECTIONS WITH THE LOWEST FORMS OF 

 ANIMAL LIFE. 



The protozoa, the lowest forms of animal life, have 

 hitherto taken part in the etiology of but a small number 

 of diseases in human beings. Perhaps the future will show 

 that they occupy a larger field of activity. In a number 

 of infectious diseases whose exciting agents are as yet un- 

 known, animal parasites are believed to have been observed 

 as, for instance, in whooping-cough, in carcinoma, and 

 others. The connection of disease with the lowest forms 

 of animal life has, however, been established with certainty 

 only for two affections namely, dysentery and malaria. 



DYSENTERY (AMEBIC ENTERITIS) AND TROPICAL AB- 

 SCESS OF THE LIVER. 



The cause of dysentery was recognized by Losch in 

 1871 as peculiar animal parasites belonging to the class of 

 protozoa amebce which were found in dysenteric stools. 

 Koch, on the occasion of his cholera-expedition to Egypt, 

 noted the same organisms in the base of the ulcers of the 

 intestine in four fatal cases of dysentery. Kartulis, Ogata, 

 and others, and in Germany recently Kruse and Pasquale, 

 and, further, Quincke and Roos, have since studied the 

 amebse carefully, and confirmed their etiologic relation to 

 dysentery. 



Th amebae of dysentery are unicellular organisms of 

 varying size, with ameboid movement. The smallest cells 

 are about 10 fj. in diameter ; the largest, 50 (J. (giant amebce) ; 

 the majority, at rest, from 20 to 25//. The protoplasmic 

 body of the amebae can be differentiated on movement into 

 an outer zone, the ectoplasm, which is homogeneous and 

 less refractive, and the entoplasm, which in part is appar- 

 ently almost structureless, containing a small number of 

 disseminated granules and differentiated from the ectoplasm 

 only by its greater refractive power, and in part highly 

 granular, and completely filled with irregular, mostly quite 

 fine granules (granular plasma), or, finally, exhibiting a 

 greater or lesser number of large and small vacuoles. The 

 two layers are distinctly differentiate from each other only 

 when the ameba is in motion, while the differentiation is 



