220 GENERAL ANATOMY. 



insensible, and at others liquid and visible; in the latter cat>e 11 

 is called sweat. This secretion is continual, and probably, es- 

 sentially the same in both cases; but in the first it is insensible 

 on account of its vaporisation. The secretion takes place in 

 the skin, but by what vessels, we do not know; as to the 

 ways by which it traverses the corpus mucosum and the epi- 

 dermis, we are totally ignorant. It is likely that the perspi- 

 ratory secretion takes places in the bottom of the microscopic 

 incisures and depressions of the epidermis, a place where it 

 is the least dry. The quantity of this secreted matter is very 

 great, but difficult to determine. Sanctorius, whose experi- 

 ments are so celebrated, had observed, that he lost five-eighths 

 of the whole of his aliment by pulmonary and cutaneous per- 

 spiration. Among those who have repeated his experiments, 

 Lavoisier and M. S6guin have made this distinction; they 

 found that the cutaneous perspiration, is to the pulmonary 

 perspiration on an average, as eleven is to seven. Cruikshank 

 has tried to determine its nature, and found that it had all the 

 properties of water, containing carbonic acid and an odorous 

 animal matter. 



When the matter of perspiration is collected in the form of 

 sweat, we see it appear on the surface of the skin in small 

 drops, upon which Leuwenhoeck has made some interesting 

 observations. Human sweat in a state of health is always 

 acid, saltish, and odorous. According to Theuard it is formed 

 of much water, a small quantity of acetic acid, of hydro chlo- 

 rate of soda, and perhaps of potash, very little earthy phos- 

 phate, an atom of the oxide of iron, and of an inappreciable 

 quantity of animal matter. M. Berzelius considers it as water 

 holding in solution the hydro chlorates of potash and soda, 

 lactic acid, lactate of soda, and a little animal matter. 



The cutaneous perspiration, either sensible or insensible, 

 must be regarded as one of the most important excretions of 

 the organism. It is, besides, a potent mean of refrigeration 

 and of resistance against too elevated a temperature. This 

 function presents numerous varieties, according to the age, 

 sex, the individual, external circumstances, the state of the 

 other functions, the action of ingested or applied substances, 



