GROUP OF THE CUTANEOUS SECRETIONS 897 



the elimination of water by the kidneys, and vice versa. Both of 

 these processes are related in turn to the intestinal secretions, because 

 watery stools are invariably associated with a diminished excretion of 

 water by the. other channels. 



The Innervation of the Sweat-Glands. — The sweat-glands are 

 richly supplied with nerve fibers, some of which are doubtlessly secre- 

 tory in their nature. They perforate the membrana propria and form 

 mulberry-like end-organs directly upon the outer surfaces of the cells. 

 According to Langley,^ those innervating the glands of the cat's 

 hind limb leave the spinal cord in the first and second lumbar nerves, 

 enter the sympathetic system and leave it again in the gray rami 

 of the sixth lumbar to the second sacral nerves. Their chief outpour- 

 ing takes place in the seventh lumbar and first sacral rami. All of 

 them enter into the formation of the sciatic plexus. A similar out- 

 pouring occurs between the fourth and tenth thoracic nerves, the fibers 

 of which eventually enter the brachial plexus. 



The presence of these secretory fibers has been demonstrated by 

 Goltz^ who stimulated the distal end of the divided sciatic nerve and 

 observed drops of sweat appearing upon the hairless skin covering the 

 balls of the feet. This effect may also be evoked after the ligation of 

 the abdominal aorta as well as after the amputation of the leg, but 

 naturally, only a very limited amount can then be obtained, because 

 the cells are no longer able to acquire new secretory material. Under 

 normal conditions, this nervous mechanism is activated by rises in 

 the temperature of the atmosphere as well as by increases in the blood- 

 pressure following muscular activity and increases in the water con- 

 tent of the body. Furthermore, many factors are constantly at work 

 which tend to vary the amount and character of this secretion. It is 

 a well known fact that the skin in fever is dry and that the subsequent 

 reappearance of the sweat is generally accompanied by a fall in the 

 body-temperature. In other words, a moist skin is a favorable diagnos- 

 tic sign, because it facilitates heat-dissipation. Profuse sweating is 

 frequently associated with dyspnea, nausea and psychic impressions 

 of terror. Among the drugs which influence the character of this 

 secretion should be mentioned pilocarpin and atropin. The former 

 stimulates its flow by acting directly upon the terminals of the secre- 

 tory nerves, while the latter diminishes it by paralyzing these endings. 

 Alcohol produces a dry skin and nicotine a moist skin. Cold lessens 

 the secretion, because it gives rise to a reflex constriction of the cutan- 

 eous blood-vessels. 



The Mammary Glands. — Each fully formed mamma consists of 

 15 to 20 lobes, which are composed of lobules and the latter in turn of 

 numerous groups of cells or acini. The smaller ducts emerging from 

 these eventually unite into a large lactiferous duct which opens 

 through the nipple. Externally to their point of union the different 



1 Jour, of Physiol., xii, 1891, 347. 



2 Pfluger's Archiv, xi, 1875, 71. 

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