358 EXCRETION BY THE SKIN AND KIDNEYS. 



The sweat is exhaled usually in the form of 'vapor, when it is known as 

 insensible perspiration. When from any cause it collects on the surface, in 

 the form of a liquid, it is called sensible perspiration. 



The peculiar constituents of the sweat have been more carefully and suc- 

 cessfully studied since the analyses of Favre. The neutral fats are probably 

 derived in great part from the sebaceous glands, although certain fats, palmi- 

 tine and stearine, have been found in the secretion of the palms of the hands, 

 which contain no sebaceous glands. The volatile fatty acids are formic, 

 butyric, caproic, capric, acetic etc., some of which exist also in milk. These 

 give to the sweat its peculiar odor. Urea is always present in small quan- 

 tity, and its proportion may be largely increased when there is a deficiency of 

 elimination by the kidneys. It is a matter, also, of common as well as of 

 scientific observation that the sweat is more abundant when the kidneys are 

 comparatively inactive, and vice versa. Generally, however, conditions oper- 

 ate to increase the quantity of sweat, and the quantity of urine is proportion- 

 ally diminished. The skin is undoubtedly an important organ of excretion, 

 and it may eliminate excrementitious matters of a character as yet unknown. 

 The action of the skin as a respiratory organ has already been considered. 

 With regard to the inorganic constituents of the sweat, there is no great inter- 

 est attached to any but the sodium chloride, which exists in a proportion 

 many times greater than that of all the other inorganic salts combined. 



Peculiarities of the Sweat in Certain Parts. In the axilla, the inguino- 

 scrotal region in the male, and the inguino-vulvar region in the female, and 

 between the toes, the sweat always has a peculiar odor, more or less marked, 

 which in some persons is excessively disagreeable. Donne has shown that 

 whenever the secretion has an odor of this kind its reaction is distinctly alka- 

 line ; and he is disposed to regard its peculiar characters as due to a mixture 

 of the secretion of the other follicles found in these situations. Sometimes 

 the sweat about the nose has an alkaline reaction. In the axillary region 

 the secretion is rather less fluid than on the general surface and frequently 

 has a yellowish color, so marked, sometimes, as to stain the clothing. 



PHYSIOLOGICAL ANATOMY OF THE KIDNEYS. 



The kidneys are symmetrical organs, situated in the lumbar region, be- 

 neath the peritoneum, invested by a proper fibrous coat, and always sur- 

 rounded by more or less adipose tissue. They usually extend from the 

 eleventh or twelfth rib downward to near the crest of the ilium, and the 

 right is always a little lower than the left. In shape the kidney is very 

 appropriately compared to a bean ; and the concavity, the deep, central por- 

 tion of which is called the hilum, looks inward toward the spinal column. 

 The weight of each kidney is four to six ounces (113 to 170 grammes), usu- 

 ally about half announce (14 grammes) less in the female than in the mala 

 The left kidney is nearly always a little heavier than the right. 



Outside of the proper coat of the kidney, is a certain quantity of adipose 

 tissue enclosed in a loose, fibrous structure. This is sometimes called the 

 adipose capsule ; but the proper coat consists of a close net- work of ordinary 



