OCTOBEB 14, 1910] 



SCIENCE 



511 



Three pheasants were infected with coccidia 

 but the livers are not mentioned. In two 

 quail the typical lesions of blackhead were 

 present in intestines and liver, the organism 

 being found both in the tissues ( ?) and the 

 intestinal contents. In one grouse coccidia 

 were found. The liver is not mentioned. 



Of seventeen pigeons all of which died, some 

 with symptoms of coccidiosis, the organisms were 

 found in nine and were usually accompanied by 

 such lesions of either intestines or liver that a 

 diagnosis of coccidiosis was justifiable. In several 

 of the other eight pigeons, lesions which resembled 

 those of blackhead were found both in intestines 

 and liver, but apparently not accompamied hy 

 coccidia. 



Sjobring,' who studied coccidiosis among 

 birds in Sweden, describes forms belonging 

 to two genera of coccidia. The one, evidently 

 the predominating if not the only one ob- 

 served by Cole and Hadley and by me, was 

 found by Sjobring in pheasants. The other, 

 characterized by the presence of two instead 

 of four spores, was encountered in many dif- 

 ferent species of birds. The author states dis- 

 tinctly that he found neither kind in the 

 liver. 



Since the writer's work in 1894 the entero- 

 hepatitis of turkeys has been encountered in 

 the common fowl. It seems as if this parasite 

 of turkeys had adapted itself to fowls and to 

 other species of birds. In the above quota- 

 tions from Cole and Hadley's work we see 

 enough uncertainty to make us believe that 

 the authors saw now one disease, now the 

 other, now both together in different birds 

 without distinguishing between them. 



There is thus ample evidence to show that 

 entero-hepatitis may run its course in a 

 flock without the presence of a single coc- 

 cidium cyst to suggest coccidiosis. On -the 

 other hand, it is evident that coccidiosis 

 among birds has been frequently seen during 

 the past thirty years, but without involvement 

 of the liver. Finally a double infection seems 

 to have been the rule at the Rhode Island 

 Experiment Station, where the work of Cole 

 and Hadley was done and where the animals 

 used in the experiments were reared. 



^ Centralbl. f. Bakt., Erst* Abth., 1897, 22, p. 

 675. 



This simple fundamental statement must 

 suffice for the present. Aside from this there 

 are many reasons why A. meleagridis and C. 

 tenellum should not be regarded as identical. 

 The former organism has no morphological 

 characters which even remotely suggest a 

 coccidium, and its situation and mode of at- 

 tack upon the tissues are likewise wholly dif- 

 ferent from those which accompany coccidi- 

 osis. To state more than this would require 

 a minute analysis of many pages of text in 

 which the writers have laboriously endeavored 

 to explain why true coccidia are met in some 

 cases and not in others. If we should try to 

 describe kangaroos and zebras intermingling 

 in an enclosure, now in terms of one, now in 

 terms of the other by assuming a genetic re- 

 lationship between them, we would be in the 

 same predicament in which the authors find 

 themselves. To attempt to correct matters 

 would be impossible. 



It is obvious that in pathological work it is 

 important to distinguish between lesions of 

 difFerent character, for they are of great serv- 

 ice in the study of causation. In biological 

 research it is far more important to keep 

 morphological entities apart than to throw 

 them together, unless very good reasons ap- 

 pear for identifying them. It is always pos- 

 sible for our successors to put them together, 

 whereas a separation is impossible when a 

 single term such as " blackhead " or coccidi- 

 osis is used to cover all. Eivolta had the 

 same problem before him when first describ- 

 ing avian coccidiosis.' 



In 1873 he noticed in the intestinal wall of 

 fowls, dead of disease or killed, white points, 

 the size of a poppy seed, found in the sub- 

 mucous connective tissue. These were small 

 cysts full of "navicellfe" (merozoites?). In 

 1878 he saw in young chickens a disease, 

 characterized by emaciation, diarrhoea, pallid 

 flesh, etc., and by the presence of large num- 

 bers of minute white points in the duodenum. 

 They appeared to be in the submucosa. In 

 the intestinal contents many oval psoro- 

 sperms (coccidia cysts?) were found. Eivolta 



' " Delia gregarinosi dei polli, etc.," Oiorn. di 

 anat. fisiol. et patoJ. degli animali, Pisa, 1878, X., 

 p. 220. 



