88 MAMMALIA. 



bat's wing membrane consists of two sheets of skin, the upper de- 

 rived from that of the back, the lower from that of the belly. The 

 epidermic and Malpighian layers in each sheet remain separate, 

 whilst the true skin is inseparably fused. In this fused medium 

 layer are imbedded the muscles, nerves, vessels, etc., of the wing. 

 The whole wing is covered, both on the upper and 

 under surface, with extremely fine, sparsely scattered hairs. . . . 

 Each hair sac has from two to seven sebaceous glands, according 

 to the species, and one sweat gland opening into its sac. The two 

 outer fibrous layers of the hair sac have no sharp line of demarca- 

 tion to separate them from the surrounding connective tissue, but 

 the inner or h)aline coat is highly developed, and, after being con- 

 stricted beneath the hair bulb, widens out and encloses the sense- 

 bodies (Tastkorperchen), one of which organs is connected with 

 each hair. 



" The nerves of the wings may be considered to consist of five 

 layers, i. e., there is one occupying the centre of a transverse sec- 

 tion of the wing, which gives off on each side of it four others, and 

 these are successively finer and finer as they approach the opposite 

 surfaces. The inner layer and the one immediately on each side 

 of it, consist of nerve fibres with dark borders, the other layers of 

 pale fibres only. The tastkorperchen are connected with the second 

 layer. The fifth layer of finest fibres ends as a network between 

 the innermost layer of cells of the Malpighian layer of the epidermis. 

 The tastkorperchen are shaped like a fir-cone with a rounded apex 

 turned inwards. They lie immediately below the root of the hair ; 

 and their core or central substance is formed of a prolongation of 

 the cells forming the two root sheaths of the hair. Their length 

 is 0.0259 and their breadth 0.0175mm. A nerve containing about 

 six dark-edged fibres is distributed to each kijrperchen. Just 

 before the nerve reaches this organ it splits into two, and three 

 fibres pass to one side of it, three to the other. The fibres are 

 then wound round the body so as to sheathe its cellular core. Dr. 



