188 EXPERIMENT STATION RECORD. 



generalized coccidiosis among other domestic birds of all ages, being most 

 destructive among tbe young. The symptoms are voluntary isolation, stupor, 

 loss of appetite, drooping of tbe wings, and emaciation ; recovery is infrequent. 



A detailed account of tbe etiology of tbe disease is tben entered into. "Cer- 

 tain of tbe 'bodies' [found] are identical with the Amceha melcagridis de- 

 scribed by Smith as the cause of blackhead. In tbe majority of cases they are 

 not amebas, but stages in tbe development of a coccidium. This organism is 

 tbe cause of the majority of cases of so-called blackhead, although other or- 

 ganisms frequently produce somewhat similar pathological conditions." Tbe 

 characteristics of the coccidium are described. " The same coccidium in tbe 

 cyst stage was found repeatedly in chicks, fowls, pigeons, ducks, geese, pheas- 

 ants, guinea fowl, quail, grouse, sparrow, thrush, robin, junco, mice, and rats, 

 and probably in rabbits. In many of the birds mentioned above, and in tbe 

 rabbit, a characteristic coccidiosis was frequently observed. This was espe- 

 cially true of young brooder chicks, in which the coccidium is one factor in 

 the disease commonly called 'white diarrhea.' In this disease and in some 

 other varieties of coccidiosis, it is important to observe that coccidiosis may 

 be highly active without tbe presence of the encysted stage. 



" The infective cycle is probably, in most cases, initiated as tbe result of tbe 

 ingestion of a certain number of cysts. These, probably acted upon by the 

 digestive fluids of the small intestine (pancreatic secretion), liberate tbe sporo- 

 zoites, which at once enter epithelial cells. The sporozoites develop into 

 schizonts, which liberate the merozoites, and these, in turn, develop into other 

 schizonts. This schizogenous cycle is maintained for a certain time before tbe 

 merozoites, instead of forming more schizonts, develop into the sexual products 

 (macrogametes and microgametes). Tbe sexual elements unite and the product 

 (oocyte) develops into the permanent cyst. During these cycles of develop- 

 ment, many epithelial and connective-tissue cells are broken down, and this 

 disintregation i-esults in the characteristic pathological changes mentioned above. 



" Experiments in transmission showed that blackhead could be transmitted 

 by feeding from poult to poult, from poult to chick, and from chick to poult. 

 In all these cases permanent cysts were present in the material which was used 

 for feeding. It is not known whether the disease can be transmitted by other 

 stages in the development of tbe coccidium. Experiments in transmission indi- 

 cate further: (1) That blackhead may be transmitted by association and, in 

 all probability, through the egg; (2) that bird lice and earthworms probably 

 play no part in transmission." 



"Although experimental work on the prevention and treatment of blackhead 

 has advanced but little, a few preventive measures are recommended;" these 

 include the protection of yards in which uninfected flocks are kept, the isola- 

 tion of turkeys from other domestic fowls, the immediate isolation of birds 

 which give evidence of the disease, tbe protection from English sparrows, rats, 

 etc., which may carry the causative agent, a gradual increase of rations when 

 fattening, and prompt incineration or burial of fowls dead from the afliection. 



A bibliography of literature relating to tbe subject is appended. 



The gospel of cleanliness for poultrymen, G. B. Morse (Rcl. Poultry Jour., 

 J7 {1910), -So. 8, pp. 756, 757, 775-777, figs. 7).— An address delivered before tbe 

 American Poultry Association at St. Louis, August 18, 1910. 



The chief points worthy of note are tbe author's maxims, which are as fol- 

 lows; "(1) Clean out tbe birds by means of Epsom salts, administered in an 

 evening mash, estimating one-third of a teaspoonful to each adult bird. (2) 

 Clean up by spreading powdered slaked lime over runs, dropping-boards, and 

 floors of houses. (3) Clean water supply, to be obtained by adding perman- 

 ganate of potash, enough to give it a claret red color. (4) Clean food, secured 



