13 



worm eggs on a single occasion, which rapidly produce a 

 quantity of young worms, causes an injury which allows the 

 blackliead parasite to penetrate the tissues. It is also possible 

 that such conditions may occur in nature when young turkeys 

 rather suddenly acquire a large number of parasitic worm eggs. 

 On the other hand, the cases of natural blackhead associated 

 with few or no worms suggest that there may be conditions, 

 other than those resulting from the presence of worms, which 

 favor blackliead. The point to be emphasized is that we know 

 that the ingestion of an excess of worm eggs will probably 

 produce blackliead. 



Before continuing to the practical application of the estab- 

 lished facts concerning blackhead to the problems of turkey 

 raising, it may be well to summarize the results of investiga- 

 tions to date : — 



1. The exposure of healthy young turkeys to those having 

 blacldiead does not regularly produce the disease in the former. 

 It is possible that sick turkeys are no more of a menace than a 

 flock of common fowls or old turkeys. 



2. Practically all turkeys are susceptible to blackhead, as 

 may be demonstrated by experimental inoculation. 



3. The feeding of large numbers of the ripe eggs of the in- 

 testinal worm, Heterakis papillosa, is followed by blackhead. 



4. Turkeys may acquire naturally a considerable number of 

 worms without developing blackhead. 



5. Under natural conditions, while blackhead is commonly 

 associated with a large number of worms, cases sometimes 

 occur in which there are few or no worms. 



What is the practical bearing of these experimental findings? 

 Everything points to one basic principle, and that is isolation 

 for young turkeys. To what extent isolation will be effective 

 with respect to the acquisition of the parasite of blackhead we 

 do not not know, but this is certain, that isolation will be 

 effective in keeping down the worm population in young turkeys. 

 By isolation we do not mean nominal isolation with an old 

 turkey or with an old hen, or isolation for a month and then 

 allowing the brood to mingle with the other inhabitants of the 

 farmyard. We do not deny that it is sometimes possible to 

 "get by" with such makeshift isolation; in fact, probably the 

 great majority of present-day turkeys are raised under just 



