116 DISEASES OF DOMESTICATED BIRDS 
are known to be capable of penetrating the egg shell and developing 
in the albuminous material with consequent destruction of the em- 
bryo. The aspergillus colony may be observed as a dark spot on 
the internal membrane of the air chamber. Infection through this 
source is no doubt rare. It may be guarded against by using clean 
straw or chaff in nests for laying or sitting hens, and by dipping 
eggs for hatching in grain or wood alcohol before incubating. 'eed- 
ing discarded eggs to young chicks is dangerous since these may 
carry the causative organisms of several diseases. 
FAVUS 
Synonyms. White comb; favus de la poule (French); Weisser 
Kamm (German). 
Characterization. Favus is a contagious, chronic disease of the 
skin characterized by the presence of white areas most commonly 
localized on the head and is caused by a fungus. 
Etiology. The fungus causing the disease is designated Lopho- 
phyton galline. It grows readily on agar containing 1 per cent 
peptone and 4 per cent of glucose or maltose at room temperature 
when the medium is seeded with material from the diseased patches. 
Growth first appears as a small, round, pure white, downy colony. 
As it enlarges it takes the form of a button which is slightly cup 
shaped. The culture ordinarily remains white if kept at a low 
temperature. At 27° to 37° ©. the colony takes on a delicate rose 
color, becomes umbilicated, wrinkled and divided into sectors by 
lines radiating from the center. At 30° C. the culture is wholly 
rose colored, but more or less deep depending upon the culture. 
Sometimes the color varies in the same culture tube. The diffusion 
of the raspberry color in the medium is said to be an exclusive char- 
acter of the species in question. 
Pathogenicity. The infection is readily transmitted to a fowl 
by rubbing the comb with scales from a diseased bird. The disease 
is unmistakably present on the fifteenth day after inoculation and 
persists for months. Similar results are obtained with cultures. 
Mice, rabbits, guinea pigs and man are susceptible. Infection may 
occur through direct or indirect contact. ° 
Symptoms and morbid anatomy. The disease first appears on 
the head and its appendages such as the comb, wattles and barbs. 
Nearly always the initial lesion is in the vicinity of the beak, in the 
form of numerous small white points. Under a magnifying glass 
