No. 631] SHORTER ARTICLES AND DISCUSSION 177 



that it may be necessary to change this when the nature of the 

 parasite is better understood. ' ' The present writer would prob- 

 ably have been more cautious in his original criticisms of Dr. 

 Smith's conclusions if that statement had been made by Dr. 

 Smith in 1895 instead of 1915. This will answer a criticism of 

 Dr. Tyzzer's that is rather subtle and only implied. 



Again, it is implied that something must be wrong with an 

 investigation that purports to demonstrate that Trichomonas is 

 the causative agent in an infection, when the investigator can 

 not put his finger on the species concerned, or even risk the 

 foundation of a new species. Who will come forward and give 

 us a clear, definite and usable classification of the Trichomonads ! 

 And, speaking of new species in such a poorly known group, one 

 can not help wondering if it would not have been just as well, in 

 an earlier case, to leave the " meleagridis" off of Ameba. Can 

 one doubt that many unhappy hours and profitless discussions 

 have resulted from the necessity of piling up premature ad- 

 jectives after an innocent Latin noun? Why embarrass the 

 lexicographers until we are sure? And in the case under con- 

 sideration the present writer wasn't sure. 



Again Dr. Tyzzer states that it is obvious that the present 

 writer "does not consider the organism as primarily pathogenic 

 in nature, but as a normal inhabitant of the alimentary tract of 

 turkeys and fowls which may invade the tissue under conditions 

 which lower the resistance of the host." This is quite true. 

 Then Dr. Tyzzer continues, 



Apparently this author attaches no importance to the fact that the 

 disease may be produced in healthy flocks by the introduction of in- 

 fected birds. 



This is also quite true. The writer does not know of a care- 

 fully controlled experiment in which it has ever been conclusively 

 demonstrated that blackhead has been produced in healthy flocks 

 by the introduction of infected birds. During one year of ex- 

 perimental work in the field the writer made it a point of remov- 

 ing the ceca and livers of poults which died of blackhead, chop- 

 ping them up in a meat cutter, mixing lightly with middlings 

 and feeding en masse to other poults as a partial substitute for 

 beef-scraps. The mortality from blackhead in the fed group 

 and in the control group was essentially the same. Most of the 

 poults died after several weeks with gape-worm infection, and 

 with no sign of pathologic changes in either ceca or liver. The 



