178 



THE A.MKIUCAX XA ICR A LI ST 



[Vol. LIV 



writer would have no apprehension in feeding to "healthy" 

 poults any reasonable amount of pathologic material from black- 

 head cases, provided it were done in such a way as not to upset 

 the normal digestive equilibrium, and not to introduce pathogenic 

 bacteria nor bacterial toxins. 



If Dr. Tyzzer had seen as much of blackhead in the field and 

 on the farm as he has seen in the laboratory, he might more 

 readily find reason in the writer's viewpoint. Until a few years 

 ago, the writer held strongly the same views which Dr. Tyzzer 

 now holds. But here, as in some other branches of science, " field 

 work" and field experience has often wholesomely corrected mis- 

 guided laboratory theory; at least the writer has found it so in 



In another place Dr. Tyzzer states : 



Contrary to Hadley's claim Anuria nwleayridis should not be re- 

 garded as a cell parasite. ... It does not occur within cells except after 

 motility is lost, when it is soon phagocyted. 



Regarding the matter of cell-invasion Dr. Tyzzer quotes from 

 a passage from the author but stops prematurely. The passage 

 should be read as a whole to obtain the writers' full meaning. 

 The writer states that, in tissue-invasion, we see Trichomonas in 

 a new role, and that here it may actively invade living cells. At 

 this point Dr. Tyzzer 's quotation stops, but in the original ihe 

 text proceeds: 



One may remark that the type of cell invaded is a highly specialized 



The writer points out elsewhere that this invasion is not 

 passive but active. But nowhere in any of Ids published papers 

 (except in reference to the "goblet" cells) does the writer give 

 any expression of the opinion that Trichomonas is a cellular 

 parasite in the same sense that applies to the coccidia or other 

 sporozoa. In this respect, Dr. Tyzzer accidentally misrepresents 

 the writer's views. Such little mistakes as always likely to 

 happen in the hurried reading of long and complicated papers. 



A further criticism of Dr. Tyzzer 's is too good to omit.. The 

 circumstances are as follows : Tin- epithelium of the cecum of the 

 turkey is thrown into folds. Sometimes they are deep and some- 

 times shallow. Within the folds, next to the cecal wall, are the 

 crypts. The projecting folds, w ith their accompanying 



