238 SKIN, HAIR, AND NAILS, BY ALFRED BIESIADECKI. 



The development of the sebaceous glands commences at the 

 third month in Man, by the formation of a projection of the 

 cells forming the external root-sheath at the level of the future 

 gland. These epithelial cells subsequently increase in number, 

 and then appear as a pyriform process of the root-sheath. 



SWEAT GLANDS. 



Sweat glands (glandules sudoriparce) are tubular glands 

 contorted into a knot, and opening on the surface by a straight 

 excretory duct. In each sweat gland, therefore, we must 

 distinguish between the gland knot and the excretory duct. 



The gland knot (fig. 191) forms a small, roundish, yellow 

 body, which almost always lies in the subcutaneous connective 

 tissue, but is occasionally found in the lowermost parts of the 

 corium. Its diameter is usually from 0*15 to 0*5 of a milli- 

 meter. Those of the axilla measure from one to two millimeters, 

 and a few even as much as five millimeters. 



In the glomerulus the tubular duct of the gland is much 

 contorted, and held together by loose connective tissue. The 

 blind end of the tube lies in the centre of the knot, and is 

 somewhat enlarged, measuring in one case three-fourths of a 

 line (Krause). 



The gland tube is composed of a sheath, lined by enchyma 

 cells. The sheath is a delicate transparent membrane, that, 

 when acted upon by nitrate of silver, exhibits areas in which 

 are oblong nuclei (Czerny). 



The loose connective tissue between the windings of the tube 

 is composed of fine, fibres that run parallel to it, and contains 

 scattered fusiform connective-tissue corpuscles. It forms a 

 kind of capsule around the gland knot, and is traversed by a 

 narrow-meshed vascular plexus. 



In the larger glands, as in those of the axilla, numerous 

 longitudinal muscle cells lie on the outside of this membrane, 

 giving a striated appearance to the surface of the gland. 



The gland tube is lined by a single layer of conical or 

 columnar cells. 



Inasmuch as the gland knot lies in the subcutaneous con- 

 nective tissue, the excretory duct of the sweat gland must 



