7() m ^— t M f% i^mm^i r- a* x 



a oeiieration different from, und foregoing to, the generations to be passed in tlie 

 liver. 



If the eonsiderations above given are vaHd, the progressing process of the 

 disease may be assumed as follows : in the first stage, the hepatic cells are more or 

 less destroyed ; in the second stage, the hepatic tissue is turned into fibrous retic- 

 ulum, the gland cells being totally absorbed ; in the third stage, the reticular struc- 

 ture disappears to a large extent, and the parasitic cells can no longer be detected 

 there jit all ; while in the fourth stage, the fibers constructing the abnormal tissue 

 is converted into an almost homogenous plate. When the liistological changes of 

 the last state advance to a certain extent, then the death of the host animal takes 

 place. 



The parasites escaped through the bile-ducts are, it is obvious, cast oft", together 

 with the excrement, through the vent. They are probably encysted in the exterior 

 to be again taken up, mixed with foods, by other host individuals wliich will be 

 infected bv them. 



Part II. HISTORICAL REVIEW AND CONCLUDING REMARKS. 



It is rather curious that the sti 'Icing disease of the turkey above referred to 

 has drawn the attentifni of comparatively a few scientic observers. So far as I 

 am aware, concerning the disease in question, there are only a few published papers, 

 of which the work by Cusliman,-^ that by Smith -^ and that by Moore ^'' are very 

 well known. The views advanced by these three authors are in accordance in 

 concluding that the bacteria which are found in the diseased organs of the turkey 

 in large number, can by no means be looked upon as the pathogenetic in the disease 

 imder consideration. As mentioned in the foregoing pages, the results of my present 

 work also speak for this view. As to the real cause of the disease, on the other 

 hand, the results arrived at by myself best agree, as seen from the above desci-iptions, 

 with those by Smith,^^ but I can not, at present, determine with certainty, 

 whether or not the parasite represents the species named by Smith. In spite of 



1) Cushman: Nature of Black Head in Turkeys: Reports of Ehode Island Agr. Exp. Station, p. 

 199, 1894. 



2) Smith: Infectious Entero-Hepatics in Turkeys: Bulletin of the Buroan of Animal Industory, 

 U. S. A. Dep. of Agr. No.8. 1895. 



.'V) Moore : The direct Transmission of infectious Entero-Hepatics in Turkeys: Circular Xo. ö. 

 Bureau of Animal Industory, U. S. A. Dep. of Agr., No."., 1896. 

 4) Loc. cit. 



