STEUCTURAL CHARACTERISTICS OF THE 

 HAIR OF MAMMALS 



DR. LEON AUGUSTUS HAUSMAN 

 Zoological Laboratory, Cornell University 



The microscopic structures in the hairs of mammals 

 offer certain definite and unchanging characteristics 

 which have been found useful for the purposes of iden- 

 tification. 1 The present paper aims to be an answer to 

 numerous inquiries which the writer has received re- 

 garding: (1) the structure of a large number of mam- 

 mal hairs, with especial reference to the possibility of 

 systematically classifying them upon some morphologi- 

 cally accurate basis; (22) the relationships between the 

 various elemental structures of the hair shaft; and (3) 

 the methods employed in the preparation of the hairs 

 for microscopic analysis. 



The primary development of the hair begins as a local- 

 ized proliferation of the cells of the outermost layer of 

 the skin, known as the epidermis, forming a dense aggre- 

 gation of cells which elongates downward into the 

 corium, or dermis, beneath. Directly underneath this 

 downward-elongated, flask-shaped depression of the cells 

 of the epidermis there is formed a dense mass composed 

 of cells of the corium, or dermis, which ultimately be- 

 comes the papilla of the hair (P, Fig. 178). The flask- 

 shaped depression now becomes lined with cells of the 

 epidermis, and is called the follicle. The epithelial con- 

 tents of the growing follicle elongate into an avial strand 

 of fusiform, -pindle cells, which Inter undergoes keratini- 

 zation, or becomes horny, and forms the hair shaft. The 

 lower portion of the shaft expands into a bulb which en- 



