ISOSPORA. 165 



Remarks. — The parasite named Isospora hominis (Railliet 

 & Lucet, 1901) was first discovered by Virchow in 1860. 

 Human Coccidia were observed, among others, by Woodcock 

 (1915), Wenyon (1915), Cragg (1917), Dobell and O'Connor 

 (1921), and Reichenow (1925), and referred to /. hominis, 

 but according to Wenyon (1926) all these later findings of 

 Isospora oocysts refer to I. belli and not to /. hominis, which 

 he regards as a species with small oocysts. Dobell (1926) 

 considers that the small subepitheHal form is identical with 

 the larger form in the epitheUum. He holds that the case 

 for two species is not proven, and that the name Isospora 

 hominis should be adhered to. Wenyon (1926 a) has replied 

 vigorously and adheres to his former opinion. Reichenow 

 (1929) recognizes the two species as distinct. 



Cragg (1917) reported four cases from Bombay, but all these 

 patients are beheved to have contracted the infection in the 

 Mediterranean war area. Knowles (1928) reported having 

 observed the infection in man five times during the six pre- 

 ceding years, and reported another case in 1933. Das-Gupta 

 (1934) recorded his observations on the case of a Bengah 

 Brahman from Calcutta who had never been abroad. 



Habitat. — Faeces of man : Bombay, Bombay ; Bengal, 

 Calcutta. 



96. Isospora bigemina (Stiles). (Fig. 75.) 



Corpuscles gemines, Finck, 1854. 



Cytospermmm villorum intestinalium cards et felis, Rivolta, 1874, 

 -p. 1 ; 1877, pp. 42-6, 85-8. 



Coccidiwm bigeminum. Stiles, 1891, p. 163 ; 1892, pp. 517—26 ; 

 Railliet & Lucet, 1891, p. 250 ; Labbe, 1896, p. 545 ; 1899, p. 67. 

 '\Isospora bigemina, Castellani & Chalmers, 1919, p. 473. 



Isospora bigemina, Wenyon, 1923 a, p. 257, pi. xiii, figs. 1—11 ; 

 Wenyon & Sheather, 1925, p. 10 ; Wenyon, 1926, pp. 809-13, 

 figs. 343, 344; 1926, pp. 253-66; Knowles, 1928, pp. 351-5, 

 fig. 81, 1; Reichenow, 1929, p. 957; Kudo, 1931, p. 274, 

 fig. 114 d. 



Sporogony not confined to the epithelial cells ; it usually 

 takes place and is completed in the subepitheHal tissue of the 

 viUi. In the acute stages of infection reproduction occurs 

 in the epitheU^im, and immature oocysts are passed in the 

 faeces. Oocysts of two types. The smaller ones occur in 

 both cats and dogs, while the larger ones have hitherto been 

 seen only in dogs. The oocysts ripen in the gut-tissue rather 

 than in the faeces : they have thin walls and the sporocysts 

 may escape from them and be present in the faeces and carry 

 the infection from one host to another. The sporocyst 

 contains four sporozoites and a Httle residual substance in the 

 form of a small clump or as dispersed granules. 



Dimensions. — Oocysts, smaller 8-14 /x by 7-9 fi, larger 

 18-20 /Lt by 14-16ju. ; sporocysts 13-5-15-5)u, by 9-10/i (in dog). 



