292 FAMILY: MONADID^E 



Trichomonas nature. Tyzzer (1919), however, refutes these statements, 

 and returns to Theobald Smith's original view that the invading 

 organism is actually an amoeba, and that the disease is comparable to 

 amoebic dysentery in man. Further investigations by Tyzzer (1920a) 

 showed that the amoeboid bodies which invaded the tissues exhibited 

 peculiar jerky movement when seen alive, and this fact, combined with 



(0> . •: 





Fig 137. — llistomonas meleagris from the Intestine of Turkeys affected with 

 Blackhead ( x 1,400). (After Tyzzer, 1919.) 



a. Section of large intestine, showing parasites in mucosa. b. Dividing form. 



c-d. Forms showing nuclei and blepharoplasts, with attached fibres. 



the presence of a blepharoplast from which axonemes appeared to pass to 

 the surface of the body, and the formation of a fibril between daughter 

 blepharoplasts when division occurs, strongly suggested flagellate affinities 

 (Fig. 137). Tyzzer, however, did not believe that the parasites were 

 Trichoynonas which had lost their flagella after invasion of the tissues. 

 He regarded them as aberrant flagellates, for which he proposed the name 

 IIisto?nonas meleagris, recognizing in them the bodies which Theobald 



