78 HISTOLOOY (IF TI1K rolSON-dLANDS OF 1H F( ) A(iUA. 



cells of the stratified epithelium. The slender necks of these bottle-shaped cells open on 

 the surface which separates the transition layers of the epidermis from the molt, in whose 

 separation they probably aid. 



THE CUTIS VERA. 



This layer is divided by Muhse into three zones the outer loose, the compact, and the 

 inner loose strata. This division is very plainly marked in the particular form of toad which 

 we are at present considering. The outer loose zone is a very narrow layer of tissue, just 

 beneath the stratum germinativum of the epidermis. It is very cellular and contains the 

 youngest stages of the skin glands (h'gs. 2, 3, 4, 5, <>, and 7). 



Mrs. Muhse's description of this layer is as exact for Bufa tit/ua as for the toads which 

 she studied. She says, after describing the formation of the outer loose layer from fibers 

 of the compact zone and the ascending bundles of the inner loose stratum: 



"In cither case the fibers tire very loosely arranged in a network. Fibers from the outer loose 

 layer terminate on the side toward the epidermis in numerous fine branches. This gives the appear- 

 ance of a very thin homogeneous stratum, which for the most part follows intimately the lower 

 border of the epidermis." (Muhse, he. cit., p. 330.) 







In the innermost part of this layer lie the corial melanophores (figs. 4, 5, l>, and 7). 

 These are branched cells whose cytoplasm is so heavily loaded with melanotic pigment that 

 in most cases it is impossible to see the nucleus. These cells, as Hooker (1914) has shown 

 in Rana, are amoeboid and lie in the preformed spaces in the connective tissue, which spaces 

 force upon the cell a constant form. 



The compact stratum (figs. 3 to 7) of the cutis in Btifo ayua is remarkable in several 

 ways. It consists of very compact bundles which, lunning mostly in a horizontal direction, 

 form a thick mat seven or eight times the width of the outer loose stratum. So compact and 

 closely woven are these bundles that they give to the stratum compactum the appearance 

 of an almost homogeneous mass. It is a tissue in which cellular elements are almost absent. 

 The bundles of this compact layer show a peculiar affinity for basic dyes, so that in sections 

 stained with hematoxylin and eosin the entire layer is colored dark blue (fig. 7). In sections 

 stained by Mallory's technique for connective tissue the bundles are deeply colored by the 

 aniline-blue content of the stain. The stratum compactum is broken into bundles by 

 narrow bands of connective-tissue fibers which, passing through it, unite the outer and inner 

 loose layers of the corium. 



Some of the mucous glands of the skin and the batteries of very young poison-glands 

 are found embedded in this layer and it is perforated at intervals by the ducts of the mature 

 poison-glands. Surrounding these ducts there is always found a sheath of loose tissue, 

 which has been dragged down from the outer loose corial layer during the downward growth 

 of the gland from the epidermis. In this layer of tissue the blood-vessels ascend which 

 supply the gland-ducts, the outer loose stratum of the corium, and the epidermis. 



The inner loose stratum of the corium (fig. 3) is the widest of all the corial strata and 

 contains the oldest batteries of glands. On careful examination this layer may be divided 

 into two distinct regions. About the gland acini and ducts the supporting tissue consists 

 of fine, loosely interwoven fibers and is very cellular (figs. 3, 4, 5, and 7). It seems to be a 

 continuation of the outer loose layer, with which it is identical in structure. A zone of thn 

 t issue, having a widtli of about half the diameter of the gland acinus, is found about the gland. 

 This zone contains the numerous blood-vessels which are going to the gland acinus itself. 



