41 6 Journal of Agricultural Research voi. xv, No. ^ 



Particles of the honeycomb-like crust were broken into small fragments 

 and shaken vigorously in sterile water to disintegrate the material. 

 Plates of potato-serum agar, acidified by the addition of 5 drops of an 

 Njio hydrochloric-acid solution to 10 cc. of the medium, were then in- 

 oculated with the above material. Forty-eight hours later there appeared 

 on the surface of the media grayish-white, cottony-like colonies, which, 

 when transferred to serum agar slopes at room temperature, gave a granu- 

 lar whitish growth along the stroke of the needle. After 10 to 14 days the 

 whole surface presented a frosted white appearance and became uneven. 

 The growth appeared to heap up in places, forming a finely granular 

 wrinkled appearance. It also grew down into the medium. With age 

 the growth assumed a yellowish tinge. 



The following results were noted after seeding other media: Gelatin 

 was very slowly liquefied; growth on potato was very slow; litmus 

 milk became slightly reddish in tint, but was not coagulated; growth 

 in bouillon was slow, but greatly accelerated if 0.5 per cent of raw horse 

 serum was added. In this medium the growth first occurred as a 

 membranous mass on the surface, followed by a sedimentation and 

 slight turbidity. The particles were of a flocculent nature. The bouillon 

 did not assume the uniform turbidity seen in bacterial growth. 



ANATOMICAL CHANGES 



Microscopic examination of pieces of affected comb that had been 

 hardened in alcohol, embedded in celloidin, and sectioned revealed the 

 organism in the epithelial layers and also in the cutis. Dead tissue 

 cells, leucocytes, and bacterial cells w^ere present in considerable num- 

 bers. The fungi appeared to be assembled in groups of about 10, but 

 in one case as many as 50 were observed in a group. Branching forms 

 were numerous. Growth in the tissue apparently took place by branch- 

 ing. It is possible, however, that spores were formed, although none 

 were seen in any of the specimens studied. No abscesses nor ulcers 

 were seen in any of the cases. 



Favus manifests itself clinically in the form of a dry, white, scaly 



deposit, which usually appears first on the comb and then spreads to 



the face and wattles. In advanced cases the feathered portions of the 



body are attacked to such an extent that the skin is denuded of feathers 



(Pi. 31). As long as the disease remains localized about the head the 



general health is unimpaired. In such cases the egg production does 



not seem to be interfered with. Where both the neck and body 



are involved, constitutional changes may be noted. These disturbances 



are probably the result of absorption from the necrosed epithelium and 



of bacterial invasion. There is evidently no toxin produced by the 



fungus. 



ENZOOTIOLOGY 



The first case of favus that came to our attention was in the flock on 

 a farm not far from the poultry yards of th,e experiment station. These 

 chickens were allowed to run at large, but could not come in contact 



