SEBACEOUS GLANDS. 



Fig. CXXV. 



the axilla. In this last situation, Krause found the greater number to measure from 

 one-third of a line to a line, and some nearly two lines in diameter. 



The development of the sweat-glands has been carefully studied by Kolliker. He 

 states that their rudiments, when first discoverable in the embryo, have much the 

 same appearance as those of the hairs, and, in like manner, consist of processes of the 

 mucous layer of the epidermis, which pass down and are received into corresponding 

 recesses of the corium. They are formed throughout of cells collected into a solid mass 

 of an elongated pyriform, or rather club shape, continuous by its small end with the 

 soft layer of the cuticle, and elsewhere surrounded by a homogeneous limiting mem- 

 brane, which is prolonged above between the corium and cuticle. The subsequent 

 changes consist in the elongation of the rudimentary gland, the formation of a 

 cavity along its axis at first without an outlet- 

 the prolongation of its canal through the epidermis 

 to open on the surface, and, in the mean time, the 

 coiling up of the gradually lengthening gland-tube 

 into a compact ball, and the twisting of the excre- 

 tory duct as it proceeds to the orifice. The origi- 

 nal homogeneous membrane of the duct becomes 

 thickened and is continuous with the surface of 

 the corium, whilst an epithelium appears within, 

 consisting of several layers of polygonal or rounded 

 cells. The ceruminous glands in the auditory 

 passage are known to consist of a tube coiled into 

 a rounded or oval ball, like the sweat-glands ; and 

 the investigations of Professor Kolliker show such 

 a further correspondence between the two, in 

 structure and mode of development, as to lead him 

 to regard the ceruminous glands as a mere local 

 variety of the sudoriferous, which, as above noticed, 

 present specialities both of structure and secretion 

 in particular regions of the body. 



The sebaceous glands (fig. cxxv.), pour out 

 their secretion at the roots of the hairs, for, 

 with very few exceptions, they open into 

 the hair-follicles, and are found wherever 

 there are hairs. Each has a small duct, which 

 opens at a short distance within the mouth, 

 of the hair-follicle, and by its other end, 

 leads to a cluster of small rounded secreting 

 saccules, which as well as the duct, are lined 

 by epithelium, and usually charged with the 

 fatty secretion, mixed with detached epi- 

 thelium-particles. The number of saccular 

 recesses connected with the duct usually 

 varies from four or five to twenty ; it may 

 be reduced to two or three, in very small 

 glands, or even to one, but this is rare. 

 These glands are lodged in the substance of 

 the corium. Several may open into the same 

 hair-follicle, surrounding it on all sides, and 

 their size is not regulated by the magnitude 



Fig. CXXV. SEBACEOUS GLAND 



PROM THE FACE WITH BRANCHED 

 DUCT, OPENING INTO A HAIR- 

 FOLLICLE, MAGNIFIED 50 DIA- 

 METERS (from Kolliker). 



a, epithelium continuous with 

 6, the mucous layer of epidermis ; 

 c, contents of gland ; cZ, d, the 

 groups of saccules on the branches 

 of the duct ; e, hair-follicle ; /, 

 hair. 



of the hair. Thus, some of the largest are 



connected with the fine downy hairs on the aloe of the nose and other parts 

 of the face, and there they often become unduly charged with pent-up 

 secretion. ""' 



* A few years ago it was discovered by Dr. Gustavus Simon, that the sebaceous and 



