Etiology. 833 



of the skin. Alopecia is thus, as a matter of fact, the result of 

 nutritional disturbances of the skin. 



Etiology. Alopecia seldom occurs as an independent dis- 

 ease and has in this form been noted hitherto onlj^ in horses, 

 dogs, and cattle where otherwise apparently healthy skin has 

 been permanently denuded of hair in large patches (alopecia 

 areata, Area Celsi). The symmetric occurrence of the affec- 

 tion may have a nervous cause or be due to some influence of 

 the trophic nerves. Thus Joseph saw the affection in a charac- 

 teristic form after section of the second nerve of the neck, while 

 Trendelenburg noticed falling out of the feathers in pigeons 

 after section of the sensory roots of the spinal cord. On the 

 other hand in spite of negative microscopic findings, the action 

 of parasites is not excluded with certainty. 



Holborn found a fission fiingns very siniilai- to the Trieopbyton tonsurans; 

 Sabaroud believes that the falling out of the hair is caused by a microbaeillus multi- 

 plying in the hair bulbs. 



A congenital baldness (Atrichia, Hypotrichia, or incor- 

 rectly Alopecia adnata) is seen affecting the whole surface of 

 the body in foals (Gherardi, Roder), calves (Laurent, Schaar), 

 and dogs (Corniea). This condition occasionally stands in re- 

 lation to a faulty growth of hoofs, claws and teeth (Bonnet), 

 but many a time it is inherited. Such animals usually die after 

 a short time, occasionally, however, the falling out of the hair 

 only begins 1 or 2 years after birth. 



Andre noticed general loss of hair in 11 foals of one mare, and in 8 of 

 another the hair fell out, especially on the feet and on the lower parts of the trunk, 

 near the second year of life. Roller savr a foal born without any hair, whose mother 

 had lost her hair during pregnancy. 



In by far the greater number of cases the falling out of 

 the hair is a secondary affection (alopecia symptomatica). It 

 occurs commonly in general derangement of nutrition, such as 

 feeding with fodder of bad quality, when the animals are fed 

 insufficiently, also as a result of intestinal catarrh (Duschanek) 

 or of wasting diseases such as fluke, husk, etc.; on the other 

 hand it may occur in the course of certain infectious diseases 

 (purpura, strangles, influenza, swine plague and hog cholera), 

 in which an injurious effect on the hair papillae is probably pro- 

 duced by toxins circulating in the blood. It is more difficult 

 to explain those cases in ewes, mares and bitches, where the 

 wool or hair fall out at the end of pregnancy or during the lac- 

 tation period (Hering," Spinola), also cases in horse« after se- 

 vere sweating and in individual horses as well as in large studs 

 where during several succeeding winters or summers frequent 

 cases of alopecia have occurred (Werner, Fomin, Andre). Ex- 



