5aZ A. B. DAWSON 
calary cells are seen to be radially arranged about the duct, 
giving rise to the ‘cog-wheel-like structure’ of Muhse. The 
uppermost of these cells are in direct contact with cells of the 
germinative layer of the epidermis. In perpendicular section 
the region appears as several layers of cells overlapping each 
other tile-like on either side of the gland neck (figs. 6, 12, 13, 32). 
In the granular glands they form a firm region of attachment 
for the muscle fibers extending downward over the body of the 
gland. On the mucous glands the interealary cells are usually 
less numerous, but always present. Very few authors have 
described a distinct collar for the mucous glands in other 
Amphibia. 
ec) Gland alveolus. The walls of the granular glands are 
composed of three layers. The outer, or tunica fibrosa, is made 
up of closely packed connective-tissue fibers, which interlace 
over the surface of the gland and are continuous with the fibers 
forming the bundles of the intermediate spongy layer of the 
dermis. In this region are found the highly developed elastic 
fibers already described and the nerves which supply the gland 
muscles and gland epithelium. Within the connective-tissue 
sheath lie the muscle fibers and next comes the epithelium of 
the gland. Several writers (Drasch, ’94; Junius, 96; Bruno, ’04; 
Reese, 705; Nordenskiéld, ’05) report a tunica propria present 
in other Amphibia. This they regard as a structureless mem- 
brane, comparable to a basement membrane. According to 
Schultz (89) and Weiss (’99), the glands are invested by a con- 
tinuation of the upper ‘Cutissaum,’ which was pushed downward 
by the gland during its development. But Engelmann (’72), 
Gaupp (’04), Esterly (04), and Nirenstein (’08) report a con- 
dition very similar to that in Necturus, where the gland is closely 
surrounded by connective tissue continuous with that of the 
middle dermal layer. Muhse (’09) and Shipley and Wislocki 
(15) state that in the toad the wall of the gland sac consists 
of a homogeneous matrix. The muscle fibers are inbedded in 
the outer surface of this matrix and on its inner surface lie the 
epithelial cells. 
