274 



NORMAL HISTOLOGY. 



they open by the trumpet-shaped orifices of their wavy ducts to the 

 deepest part of the reticular layer of the corium, or still farther into 

 the subcutaneous stratum, in which position the gland-tube ends as 

 a greatly convoluted spherical mass. The sweat-glands enjoy a very 

 wide distribution, being present in greater or less abundance over 

 the entire body-surface, with the exception of the deeper parts of 

 the external auditory canal and the tympanic membrane. 



The largest sweat-glands occur in the axilla, at the root of the 

 penis, on the labia majora, and around the anus. While the average 

 diameter of the gland-masses is .3-. 4 mm., the axillary glands 

 measure 2-7 mm. at their widest part. Each sweat-gland presents 

 two divisions, the greatly convoluted gland-coil and the much 

 straighter, slightly wavy excretory duct ; the former, which repre- 

 sents the secreting portion of the gland, is much wider, both in 

 its general diameter and lumen, than the part constituting the duct. 

 The gland-tube is limited by a membrana propria continuous with 

 that of the skin, outside of which a delicate connective-tissue en- 

 velope gives additional strength ; within the basement-membrane 

 cuboidal or low columnar epithelial cells form the lining of all 

 parts of the gland. In the secreting division of the tube the low 

 columnar cells are disposed as a single stratum, while those lining 

 the duct are arranged as a double layer of small and low polygonal 

 elements ; the cells of the duct are covered next the lumen of the 

 tube with a delicate cuticle. 



The duct from the secretory portion of the gland to the epidermis 

 maintains an almost constant diameter (20-25 /0 ; on entering the 

 epidermis, however, it enlarges to almost double, and on reaching 

 the stratum corium expands into the trumpet-shaped orifice which 

 marks its termination. Within the epidermis the duct loses its 

 distinct walls, the final turns of its spiral, corkscrew-like course 

 being bounded by the horny plates of the epidermis. In ex- 

 ceptional cases the sweat-glands open into the upper part of the 

 hair-follicles, but, as a rule, they reach the free surface by entering 

 the epidermis in the depressions between the papillae of the 

 corium. 



The terminal secretory segment of the gland-tube, usually 

 single, although sometimes branched, is convoluted to form the char- 

 acteristic coils, which can be seen often with the unaided eye as 

 reddish -yellow spherical masses. The columnar secreting cells 

 (10-20 jj. in height) present a single layer of elements whose pro- 

 toplasm is very finely granular and sometimes contains fatty gran- 

 ules, as well as yellow or brown particles ; these latter are espe- 

 cially evident in the ceruminous glands of the external ear, the axillary 

 and the mammary areolar glands. The nuclei of the secreting cells 



