308 JAMES EDWARD ACKERT 



NERVE LAYERS OF THE INTEGUMENT 



1 . Nerve layers of tha body integument 



In the subcutaneous tissue and in the reticular stratum of 

 the body integument, are large meduUated nerve trunks and 

 branches which, for convenience, are called the first nerve layer. 

 By dichotomous branching these nerves break up into a loosely 

 intertwined meshwork consisting of an enormous number of 

 medullated nerves. These interwoven nerves, which are not 

 :actually united in a plexus, constitute the second nerve layer 

 (fig. 4, snl). Arising from the latter are medullated nerves which 

 pass toward the periphery. Near the outer surface of the corium 

 they begin to divide. The resulting non-meduUated branches 

 pass directly to the Malpighian stratum, forming the third nerve 

 layer (fig. 4, tnl). Ordinarily so much pigment is present here 

 that it is impossible to follow the fibrils to their endings. How- 

 ever, in places where the epidermis has accidentally been torn, 

 one can readily trace the fibrils well into the Malpighian stratum, 

 noting branching fibrils which pass outward and terminate in or 

 between the cells of the stratum granulosum. As these can be 

 traced more readily in the membranes where little or no pigment 

 is present they will be considered more fully later (p. 313). Vari- 

 cosities are numerous both in the second nerve layer and along 

 the fibers which pass to the third layer (figs. 14, 15, 16, 17). The 

 greater number of these enlargements, however, occurs on the 

 smaller fibers. Varicosities in the third nerve layer, that is, on 

 the surface of the corium or in the Malpighian stratum, have 

 not as yet been observed by the writer. As the literature on nerve 

 layers in the skin of bats deals almost entirely with these layers 

 in the patagium, the brief historical survey will be given in the 

 consideration of the flying membrane. 



2. Nerve layers of the flying and interfemoral membranes 



As early as 1796 Cuvier called attention to the abundance of 

 nerves in the flying membranes of Chiroptera. Leydig, a half- 

 century later, while differing somewhat with Cuvier as to the 

 number of nerves present, admitted that these membranes are 

 richly innervated. 



