I 



lfl20] VETERINARY MEDICINE. 475 



K|ii(I('inioI<»g;y of blackhead in turkeys under api)roximately natural 

 conditions, T. Smith and II. \V. CuAYnir.r. i-loiir. i:.ii,t. Med., 31 {1!)20). A'o. 5, 

 pp. 633-6//5). — This is a report of field experiments made in contimiation of 

 those conducted during tlie warm season of 1910, previously noted (E. S. R., 

 37. p. 383). 



" The foresoinj; experiments in outdoor, unprotected inclosures demonstrate 

 the difliculties surrounding the rearing of turkeys. These are discus.sed from 

 another viewpoint helciw. 



" The occasional presence of coccidia, the presence of Heterakia papulosa 

 in the ceca, the occurrence of ca.ses of asperf^illosis and of cliickenpox in incu- 

 hator-bred birds which did not come in contact with other domesticated birds, 

 except in a few cases with incubator-bred chickens, show clearly that turkeys 

 are picking up from the ground material deposited by other birds. The agent 

 of blackhead must come from the same sources. 



" The field experiments show a steadily increasing concentration of the in- 

 fection from 1917 to 1919, even though the ground had been plowed and seeded 

 before use. As a result, the various groups of turlceys became infected to a 

 greater degree. The growth in the intensity of the disease may be in part 

 ascribed to an accumulation on the .soil of infectious agents during any given 

 sea.son after they had been introduced, but it is hardly acceptable as an ex- 

 planation from season to season, when the soil was either virgin, as regards 

 poultry yards, or plowed deep and seeded before use. A more rational hy- 

 pothesis is the gradual attraction of birds in larger numbers and greater 

 'variety on account of the food supply in the turkey inclosures and the more 

 intensive cultivation of the land surrounding the laboratory and animal build- 

 ings since the beginning of the experiments in 1917. 



"The intensity of the outbreaks due to the confining of young turkeys with 

 'birds over a year old which had been infected during the preceding year, 

 'or on grounds previously occupied by thenr, was in all instances much greater 

 .than in the spontaneous outbreaks. The cases amounted to nearly 100 per cent 

 'of the exposed. On the other hand, the number of cases in the control flocks 

 [ varied and was very low in some group^. It could have been kept down if the 

 ^sick birds had been promptly removed and not permitted to recover on the 

 same ground. However, the object of the experiment was not to suppress 

 'the disease, but to see to what extent it would develop. 



" It is self-evident that the results obtained apply strictly only to that part 



of the country where the experiments were made. We have at present no 



means of knowing whether the sources of infection would become more nunier- 



I ous and concentrated with a higher mean annual temperature, or the reverse. 



Only by using incubator turkeys exclusively for such tests and eliminating 



[the older turkeys and domesticated birds as carriers can the miscellaneous, at 



I present not controllable sources of the agents of this disease in different 



localities and the chances of successful rearing, be determined." 



Production of fatal blackhead in turkeys by feeding enibryonated eggs 



of Heterakis papillosa, 11. W. Grayium. and T. Smith (Jour. Expt. Med., 31 



{t920), No. 5, pp 6//7-6.7.5). — "In four experiments, three with young in- 



Icubator turkeys and one with young incubator chickens, in which the feces of 



'old turkeys from an infectious flock, kept at room temperature up to 5, 8, and 



10 days, were fed, no infection resulted. In an experiment in w'hich two of 



four young incubator turkeys used in one of the above experiments were fed 



. embryonated eggs of //. papillosa and feces of turkeys from an infectious flock 



(both contracted blackhead. Two controls remained well. Later they were 



fed embryonated eggs of H. papillosa and both contracted blackhead. In 



