OF THE SKIN; CUTANEOUS TRANSPIRATION. 



611 



Fig. 168. 



the use of the "alterative diuretics/' as suggested by Dr. G. Bird,, where (as 

 in chronic rheumatism, gout, &c.) there is reason to believe that a quantity of 

 mal-assimilated matter exists in the system, of which it is important to get rid. 

 In many such cases, indeed, clinical observation had already established the 

 benefit derivable from such medicines, without affording the rationale of it. 



4. Of ike Skin; Cutaneous Transpiration. 



646. The Skin is the seat of various secretions, for each of which it is pro- 

 vided with special organs ( 237, 238) ; but these have reference chiefly to its 

 own protection, or to some other local purpose; 

 and the only one which can be regarded as 

 truly excrementitious, is the Transpiration of 

 aqueous fluid, holding certain matters in solu- 

 tion. The elimination of this fluid from the 

 blood is effected by the Sudoriparous glandulae 

 (Fig. 168), which are seated rather beneath 

 than in the Cutis, and are diffused in varying 

 proportions over the entire surface of the body 

 ( 238). According to Mr. Erasmus Wilson, 1 

 as many as 3528 of these glandular exist in a 

 square inch of surface on the palm of the 

 hand; and as every tube, when straightened 

 out, is about a quarter of an inch in length, it 

 follows that, in a square inch of skin from the 

 palm of the hand, there exists a length of tube 

 equal to 882 inches, or 73 % feet. The number 

 of glandulae in other parts of the skin is some- 

 times greater, but generally less than this; and 

 according to Mr. Wilson, about 2800 may be 

 taken as the average number of pores in each 

 square inch throughout the body. Now the 

 number of square inches of surface, in a man of 

 ordinary stature, is about 2500 ; the total num- 

 ber of pores, therefore, may be about seven mil- 

 lions ; and the length of the perspiratory tubing 

 would thus be 1,750,000 inches, or 145,833 

 feet, or 48,611 yards, or nearly 28 miles. 

 Although a separation of fluid by this extensive 

 glandular apparatus is continually taking place, 

 yet this fluid, being usually carried off in the 

 form of vapor as fast as it is separated, does 

 not accumulate so as to become sensible. If, 

 however, from the increased amount of the se- 

 cretion, or from the condition of the surround- 

 ing air, the whole fluid thus poured out should 

 not evaporate, it accumulates in minute drops 

 upon the surface of the skin. Thus the Sudori- 

 parous excretion may take the form either of 

 sensible or of insensible transpiration; the latter 

 being constant, the former occasional. It is 

 difficult to obtain enough of this secretion for 

 analysis, free from the sebaceous and other 

 matters which accumulate on the surface of the 

 skin ; and its character can only, therefore, be 



Sudoriparous Gland from the palm of the 

 hand, magnified 40 diam. : 1, 1, contorted 

 tubes, composing the gland, and uniting 

 into two excretory ducts, 2, 2, which unite 

 into one spiral canal that perforates the 

 epidermis at 3, and opens on its surface at 

 4; the gland is imbedded in fat-vesicles, 

 which are seen at 5, 5. 



"On the Management of the Skin," 3d edit. p. 37. 



