No. 631] SHORTER ARTICLES AND DISCUSSION 179 



the writer has referred to as the villi. The author points out 

 that invasion of the submueosa is brought about by the passage 

 of the flagellates through the epithelium of the fundus of the 

 crypt, and that secondarily they invade (from behind) the villi, 

 and finally escape into the cecal lumen after pushing off the 

 cpitlirliuni of the villus tips. This phenomenon, which can be 

 followed clearly in snilable sections, the writer has referred to as 

 the stage of "reversed infection. " and has pointed out that it 

 constitutes m means whereby the parasites complete their para- 

 sitic cycle, rather than being buried and destroyed within the ' 

 tissues as stated by Dr. Smith, who is of the opinion that the 

 parasite of blackhead lacks this essential feature of perfect 

 parasitism. 



Here is Dr. Tyzzer's criticism of this exposition: 

 The fallacy of such reasoning i s quite apparent when the facts of the 

 monly involved in blackhead. 



The writer had carefully explained in the text the appearance 

 of the invaded tissues; he had pictured it by hand-drawings, and 

 more in detail by a series of photomicrographs. No one could 

 fail to understand the definite histological structure to which the 

 writer referred, whether it is properly termed a "villus," or 

 something else. Dr. Tyzzer may call the histological structure 

 what he pleases. The facts of the case with reference to Tricho- 

 monas remain the same. 



sider what Dr. Tyzzer means by the balance of his sentence 

 . . in the portion of the cecum commonly involved in black- 

 head." In the examination of hundreds of cases of blackhead 

 in turkeys and wild fowl the writer has found that blackhead 

 lesions may be initiated anywhere in the cecal wall ; there is no 

 part of the cecum that is "commonly involved" except for this 

 circumstance: the majority of the lesions are observed in the 

 distal half of the cecum. Thus Dr. Tyzzer neglects clearly re- 

 ported facts to grapple with a technical triviality in nomen- 

 clature ; and at the same time, manifestly from lack of experience 

 with many cases of the disease., misrepresents one of the essential 



