PHYSIOLOGICAL ANATOMY OF THE KIDNEYS. 395 



kidneys. The sudoric acid, obtained by decomposition of the sudorates of soda and of 

 potassa, is a nitrogenized substance, with a formula, according to Favre, who first de- 

 scribed it, of CioH 8 Oi3 K The nature of the volatile acid has not yet been determined. 

 The fatty matters are probably produced by the sebaceous glands, and the ordinary 

 nitrogenized matters are derived from the epidermic scales. With regard to the in- 

 organic constituents, there is no great interest attached to any but the chloride of sodium, 

 which, exists in a proportion many times greater than that of all the other inorganic mat- 

 ters 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 alkaline ; 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. Some- 

 times 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. The odor is probably due to the 

 presence of volatile, odorous compounds of the fatty acids, like the caproates, the vale- 

 rates, or the butyrates ; but the presence of these principles has never been accurately 

 determined. 



Physiological Anatomy of the Kidneys. 



The -urine is generally regarded by physiologists as the type of the excrementitious 

 fluids, it having no function to perform in the economy, but being simply retained in 

 the bladder to be voided at convenient intervals. All the remarks, indeed, that have 

 been made concerning excretion in general may be applied without reserve to the action 

 of the kidneys ; and there are few subjects in physiology of greater interest than the 

 process of urinary excretion, with its relations to nutrition and disassimilation. In 

 entering upon the study of the functions of the kidneys, it will be found useful to con- 

 sider certain points in their anatomy. 



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

 toneum, invested by a proper fibrous coat, and always surrounded 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 aptly compared to a bean ; and the concavity, the deep, central portion 

 of which is called the hilum, looks inward toward the spinal column The weight of 

 each kidney is from four to six ounces, usually about half an ounce less in the female 

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



Outside of the proper coat of the kidney, is a certain amount of fatty 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 the ordinary white fibrous tissue, interlaced 

 with numerous small fibres of the elastic variety. This coat is thin and smooth and may 

 be readily removed from the surface of the organ. At the hilum, it is continued inward 

 to line the pelvis of the kidney, covering the calices and blood-vessels. This coat, how- 

 ever, is not continued into the substance of the kidney. 



On making a vertical section of the kidney, it presents a cavity at the hilum, bounded 

 internally by the dilated origin of the ureter. This is called the pelvis. It is lined by 

 a smooth membrane, which is simply a continuation of the proper coat of the kidney, 

 and which forms little cylinders, called calices, into which the apices of the pyramids are 

 received. Some of the calices receive the apex of a single pyramid; while others are 

 larger and receive two or three. The calices unite into three short, funnel-shaped tubes, 

 called infundibula, corresponding respectively to the superior, middle, and inferior por- 

 tions of the kidney. These finally open into the common cavity, or pelvis. The sub- 



