HISTOMHIY <)!' TIIK r<HSO\-<;LAM>S <>! HI H> A(il'.\. /'.I 



lust beneath the compact stratum the inner loose layer is formed of a wide layer of 

 horizontally running bundles, arranged in sheets at right angles with each other, and 

 beneath the glands and the loose connective tissue about them is anothei narrow I;I\<T 

 constructed in an identical fashion. These two layers are connected by vertical bundles 

 of fibers (figs. 3 and 7), so that each mature gland and its immediately surrounding connec- 

 tive tissue lies, as it were, in one of the cells of a honeycomb-like structure formed of dense 

 bundles of connective tissue. There are many elastic libers scattered through this tissue 

 and in it are found numerous blood-vessels which supply the cutaneous glands, cut is vera, 

 and epidermis. 



From the inner loose layer numerous slender bundles of fine fibers pass outward to the 

 outer loose layer through the compact stratum, which they divide into irregular bundles. 



When this work was begun there was no thought of studying the vessels or nerves of 

 th(> skin glands and the material was not prepared for such a study, but it may be seen from 

 sections that the blood-supply is very abundant. In the lowest layer of the inner loose 

 stratum are numerous large vessels, probably forming a coarse horizontal plexus at that 

 level. From this plexus vertical branches, vasa3 recti, pass upward in the loose tissue 

 immediately about the glands, along the ascending bundles of connective tissue, and give 

 off in their ascent horizontal branches from which the blood-supply to the gland is derived. 

 These branches break up to form a very dense capillary network about the gland acinus in 

 the loose connective tissue immediately touching the gland. Some branches are given off 

 directly to supply the gland from the main plexus beneath the gland acini. A second plexus 

 occurs in the outer layers of loose tissue just beneath the corial melanophores from which the 

 blood-supply of the epidermis is derived. The connective tissue also contains many nerve 

 bundles. 



Scattered about in the lowest depths of the inner loose stratum of the corium are tiny 

 groups of corial melanophores whose presence accounts for the black flecking which is 

 apparent on the silvery undersurface of the skin when flaps of it are turned back and 

 stripped oft' from the body. 



THE POISON-GLANDS. 



Since the poison-glands of these toads and the histo-chemical reactions which they 

 exhibit are of major interest in this work, a brief discussion of the literature concerning them 

 may be appropriate here. Investigators who have studied the cutaneous glands of the 

 Batrachians differ among themselves as to whether these structures are all of the same 

 nature or whether a classification is possible on a morphological or physiological basis. 



Calmels (1838) and others have supported the theory that but one sort of gland is 

 found in these animals. Muhse is an ardent advocate of this idea. Indeed, her entire 

 paper has as a purpose the establishment of this theory on a firm basis. On the other 

 hand, many authors believe that glands of two or even four sorts exist. The criteria for 

 such differentiation are usually morphological, but, as in the case of Bristol and Hartelmex 

 (1908) and Esterly (1904), who speak of poison and mucous glands, difference 1 in secretion 

 has been used by many authors as a basis for classification. Physiological activity, then- 

 can be no question, affords a firmer, more secure basis for classifying anatomical structures 

 than a mere morphologic peculiarity, which often results from the technique used in hand- 

 ling the material studied, and we believe that this work has given, as we shall show later. 

 added evidence for the separation of the cutaneous glands of at least one species of toad 

 into mucous and poison varieties. 



