612 OF SECRETION AND EXCRETION. 



stated approximately. It has usually an acid reaction, which seems due 

 to the presence of acetic acid; and to this, or to lactic acid, we are pro- 

 bably to attribute the sour smell which it has, especially in some disordered 

 states of the system. The proportion of solid matter, according to Ansel- 

 mino, varies between 5 and 12.5 parts in 1000. The greater part of it con- 

 sists of organic matter, the larger proportion of which appears to be a protein- 

 compound in a state of incipient decomposition ; urea, however, has been de- 

 tected in this product by Dr. Landerer. 1 The remainder consists of saline com- 

 pounds ; of which the chlorides of potassium and sodium appear to be pretty 

 constantly present ; whilst muriate of ammonia, alkaline phosphates, free acetic 

 and butyric acids, and acetate of soda, have also been said to occur in it. 

 The proportion of solid ingredients would probably be found larger in the true 

 secretion of the Sudoriparous glands, if we had the means of collecting it sepa- 

 rately ; for of the whole fluid which passes off from the surface of the skin, only 

 a portion can be properly said to be secreted by these glands, a large part, as in 

 the case of the Kidneys, being the product of simple transudation ( 636). It 

 will be this part which will undergo augmentation, when a special determina- 

 tion of blood to the skin is produced by external heat ; and there is no more 

 reason to think that an increase in the amount of solid matter thus excreted is 

 induced by such agency, than that an increase in the solids of the urine can be 

 determined by ordinary diuretics ( 645). Hence the debilitating effects com- 

 monly assigned to profuse perspirations must be attributed to some other causes; 

 and these it does not seem very difficult to find. Thus, the great fatigue which 

 is experienced as a consequence of muscular exertion in a heated atmosphere, 

 may fairly be set down to the diminished activity of the respiratory process at 

 high temperatures ( 564, a) ; and the " colliquative sweating" of hectic fever 

 is obviously not a cause, but a consequence, of the debilitated state of the gene- 

 ral system. 



647. The entire amount of fluid which is " insensibly" lost from the Cuta- 

 neous and Pulmonary surfaces is estimated by Seguin at 18 grains per minute ; 

 of which 11 grains pass off by the skin, and 7 by the lungs. The maximum 

 loss by Exhalation, cutaneous and pulmonary, during twenty-four hours (except 

 under very peculiar circumstances) is 5 Ibs. ; the minimum If Ib. It varies 

 greatly, according to the condition of the atmosphere, and that of the body 

 itself; and these variations, as we shall hereafter see ( 665), have a most 

 important share in the regulation of the temperature of the body. The whole 

 amount of Cutaneous transpiration, " sensible" and " insensible," is greatly in- 

 creased by heat and dryness of the surrounding air ; for the heat occasions the 

 determination of an augmented amount of blood to the cutaneous vessels ; and 

 of the fluid which thus transudes, a large portion is carried off in the state of 

 vapor. The more the heated atmosphere is already charged with watery vapor, 

 the smaller will be the proportion of the transuded fluid that will thus " insen- 

 sibly" pass away; and the more will accumulate as "sensible" perspiration. 

 Exact observations on this point, however, are much wanting, in which not 

 merely the temperature, but the hygrometrical state of the air should be prc- 

 qisely determined ; the best hitherto recorded being those made by Dr. South- 

 wood Smith 2 at the Phoenix Gas-Works, in which the former element only was 

 carefully noted. These observations were made upon eight of the workmen 

 employed in drawing and charging the retorts and in making up the fires, during 

 which they are exposed to intense heat ; the men were accurately weighed in 

 their clothes, immediately before they began, and after they had finished their 

 work; and in the interval between the first and second weighings, they were 



1 Heller's Archiv.," band iv. p. 196. 



* "Philosophy of Health," vol. ii. pp. 391-396. 



