The (juiiiiiouiLS (jIuikIs uf ( Njiimiuii Toads. 337 



i>laii(l sacs is alwa3^s greater than the transverse and often reaches a 

 depth of I son microns, and oven as great as 1900 microns. If the 

 sacs are not crowded, they are more or less circular in the transverse 

 ])]ane. Tf they are closely associated and are affected by pressure 

 from neighboring glands, a variety of polygonal shapes arise (Fig. 

 10). The transverse diameter varies from 500 to 1200 microns. 



Wall of acinus. The gland sac consists of a homogeneous sub- 

 stance or matrix. In the i)eriphery are imbedded muscle fibers. To 

 the lumen surface are attached epithelial cells or nuclei. In some 

 cases the wall of the acinus is thin and the muscle fibers form a 

 more or les^ continuous sheath, and the epithelial cells rest closely 

 against the fibers (Figs. 44, 59, 60). In other instances the wall 

 of the sac is thick, the individual fibers are less closely arranged in 

 it and the fibers and epithelium are separated by a considerable 

 amount of matrix (Figs. 45, 47, 56, 62, 65). The nature of the 

 matrix of the acinus wall has been variously interpreted. Drasch is 

 the only investigator who has made any reference to a substance 

 which encloses the muscle fibers and on which rests the epithelium ; he 

 says that the whole is surrounded by a membrana propria. Several 

 others (Schultz, Weiss, Junius) state that the muscles rest upon a 

 membrana propria or basement membrane. Schultz further states 

 that each epidermal cell sends a foot in between two muscle fibers. 

 Mme. Phisalix says that the membrana consists of smooth muscle 

 fibers. 



]\Iuscle fibers. The muscle fibers are of the involuntary kind, 

 each elongated and spindle-shaped. An oval or elongated nucleus 

 contains a single nucleolus (Figs. 43-46, 51, 54, 61). In many in- 

 stances I have followed fibers through their whole extent and found 

 them to be single spindles. Other fibers, with one end split in two, 

 have been observed. Several writers (Drasch, Junius, Ancel) have 

 stated that the muscle fibers are divided into fibrillse at one or both 

 ends. I have never observed a similar condition in the toad. The 

 fibers are meridionally arranged and adapted to the curvature of 

 the gland body. The outer ends of a limited number of these fibers 

 extend to the outer part of the gland collar and their opposite ends 

 are overlapped by the tapering ends of other fibers. The number of 



