COMPARATIVE STUDY OF AM(EB^. 261 



found it in 50 per cent of the stools of healthy persons examined in East 

 Prussia, in 20 per cent of the stools examined in Berlin, and in 66 per cent of 

 the stools examined in the East Province. Craig (1905) found this species in 

 65 per cent of the stools examined from over 200 American soldiers stationed 

 at San Francisco, California, and Vedder (1907) found it in 70 per cent of the 

 stools of healthy natives in the Philippine Islands. Entamoeba coli, as described 

 by these authors, is round in the resting stage and opaque gray in color; the 

 ectoplasm is scarcely differentiated from and is less refrangent than the non- 

 vacuolated entoplasm; the nucleus is distinctly visible in the living amoeba, 

 is situated near the center of the organism, maintains its relative position in and 

 i,^ not deformed by the movements of the amoeba, possesses a thick nuclear mem- 

 brane, and contains a relatively large amount of chromatin; its movements are 

 sluggish and it does not injest the red blood corpuscles of its host. This 

 species reproduces by binary fission and by schizogony into 8 merozoites in 

 the vegetative stage, and by sporogomy which is preceded by nuclear reduction 

 and antogamy and which results in the formation of 8 sporozoite nuclei in the 

 encysted stage. This 8-niiclear sporocyst is the resistant stage of this amoeba 

 which serves for its transmission to a new host, in the intestine of which the 

 8 sporozoites are supposed to be developed. Schaudinn (1903) and Craig (1908) 

 found Entamoeba coli non-pathogenic for kittens. Schaudinn infected himself 

 twice with the cysts of this species without developing dysentery. 



Entamoeba histolytica Schaudinn, 1903, was first described by Jiirgens in 1902. 

 It was distinguished from Entamoeba coli by Schaudinn in 1903 and was found by 

 this author in the dysenteries of Egypt, China, and Siam, and has subsequently 

 been identified by a number of authors in the dysenteries of difi'erent countries. 

 This species, in contrast to Entamceba coli, is oval in the resting amoeba and trans- 

 parent or greenish in color; the ectoplasm is hyaline, viscid, distinct from and 

 more refrangent than the vacuolated entoplasm; the nucleus, scarcely, if at all, 

 visible in the living amoeba, is eccentric in position, frequently changes its 

 relative position in and is readily deformed by the movements of the amoeba, 

 possesses no limiting membrane, and is very poor in chromatin; its movements 

 are active and it frequently injests the red blood corpuscles of its host. En- 

 tamceba histolytica reproduces by binary fission, budding, and by the formation 

 of spores which contain chromidia derived from the nucleus and which are budded 

 oiT from the surface of the amoeba. These spores become surrounded by a hard, 

 impervious membrane and constitute the resistant stage that serves for the 

 transmission of this species to a new host. Multinuclear cysts are not developed 

 in the life-cycle of this amoeba. Schaudinn (1903) and Ctaig (1908) found this 

 species to be pathogenic for kittens. Craig obtained dysentery in 50 per cent 

 of these animals by rectal injection and in 66 per cent by feeding dysenteric 

 stools, and lesions characteristic of amoebic dysentery and containing motile 

 Entamoeha histolytica were found at the necropsies. 



Entamoeba undulans was observed by Castellani (1905), together with en- 

 tamoebce having the characteristics of Entamoeba histolytica, in a case of chronic 

 dysentery followed by abscess of the liver in a European at Colombo, Ceylon. This 

 species is characterized by a single, long, narrow pseudopod, which is shot out from 

 the body at short intervals and quickly withdrawn, and by an undulating mem- 

 brane. No observations upon its life-cycle or pathogenicity are recorded. 



Paramosba hominis was found by Craig (1906) in the stools of 6 natives in 

 the Philippine Islands in which diarrhoea, associa;ted in 3 eases with the passage 

 of a small amount of blood, was the only symptom. This species possesses the 

 distinct ectoplasm, the capacity for ingesting red blood corpuscles, and the active 

 motility of Entamoeba histolytica, but the size, nuclear structure, and encysted 



