4O2 THE SKIN AND ITS APPENDAGES. 



nucleated remains of the glandular epithelium. Whether a karyokin- 

 etic division of the nuclei occurs in this process is not known, and 

 how often the process of regeneration may be repeated in a single 

 cell is not capable of demonstration. It is certain, however, that 

 entire cells are destroyed, to be replaced later by new elements. 

 Other observers regard the secretion of milk as occurring without a 

 partial or total destruction of the secretory cells, but after the manner 

 of the secretion of other glands. This latter view seems more in 

 accord with the more recent observations. The membrana propria 

 of the alveoli appears homogeneous. Between it and the glandular 

 cells are so-called basket cells, similar to those in the salivary 

 glands. Benda regards the basket cells as nonstriated muscle 

 elements having a longitudinal direction, making the structure of 

 the alveoli of the mammary gland similar in this respect to that of 

 the secreting portion of the sweat-glands. 



The skin of the mammilla is pigmented, and the papillae of its 

 corium are very narrow and long. In the corium are also found 

 large numbers of smooth muscle-fibers, which form circular bun- 

 dles around the excretory ducts. In the areolae of the mammae 

 are the so-called glands of Montgomery, which very probably repre- 

 sent accessory mammary glands. These are especially noticeable 

 during lactation. The blood-vessels of the mammary gland, the 

 larger branches of which are situated mainly in the subcutaneous 

 tissue, form rich capillary networks about the alveoli. 



The mammaiy glands possess many lymphatics. These are 

 especially numerous in the connective -tissue stroma between the 

 lobules. The lymph-vessels collect to form two or three larger 

 vessels, which empty into the axillary glands. The mammaiy 

 gland receives its nerve supply from the sympathetic and cerebro- 

 spinal nervous systems through the fourth, fifth, and sixth inter- 

 costal nerves. The terminations of the nerves in the mammary 

 gland have been studied by means of the methylene-blue method 

 by Dmitrewsky, working in the Arnstein laboratory, who finds that 

 the terminal branches form epilamellar plexuses outside of the 

 basement membrane of the alveoli, from which fine nerve branches 

 pass through the basement membrane and end on the gland cells 

 in clusters of terminal granules united by fine filaments. The 

 nipple has a rich sensory nerve supply. In the connective-tissue 

 papillae are found tactile corpuscles of Meissner. 



The milk consists of fat globules of varying size, which, how- 

 ever, do not coalesce an attribute due to the presence of albu- 

 minous haptogenic membranes surrounding the globules. Shortly 

 before, and for some days after, parturition the milk contains true 

 nucleated cells in which are fat globules ; these are known as the 

 colostrum corpuscles. They probably represent leucocytes which 

 have migrated into the lumen of the gland and have taken up the 

 fat globules of the milk. This milk is known as colostrum. 



