670 SECRETION AND ABSORPTION B Y THE SKIN. 



matter from imbibition of water ; in the one-horned rhinoceros a gland opens on 

 the posterior aspect of each foot. 



The function of the curious gland at the back of the thigh of male 

 monotrenies, supplying its secretion by a long duct to the hollow horny spur on 

 the heel (so like in arrangement to the poison gland and fang of a snake) is 

 not known with certainty. 



There are glands in the skin of the male of the kangaroo, Halmaturus 

 ntfus, which secrete a red substance adhering to the hair, while the maxillary 

 glands of the female dwarf antelope, Ceplialoloplius pygmceus, secrete a blue 

 substance reddened by acid. 1 



CHEMICAL NATURE OF *$KIN SECRETIONS. 



(a) "Watery secretions. Naturally the composition of the sweat 

 of man and mammals has received more attention than that of other 

 skin secretions. 



Since the quantity of sweat secreted is dependent upon so many 

 conditions, it is of little value to quote the numbers obtained by 

 different observers, apart from a statement of the special conditions 

 under which the observations took place. 



There are several methods of collecting tbe sweat of the whole body, 

 or of special parts. Evaporation may be hindered by enclosing a part, 

 such as the forearm and hand, in a rubber bag, and the sweat collected 

 in a bottle tied into the lower end of the bag. 2 The subject may sit in a 

 Pettenkofer and Voit's respiration chamber (but breathe through tubes 

 to the exterior), and the water given off by the skin be calculated from 

 the readings of hygrometers in the ingoing and outgoing currents of 

 air. 3 Or the secretion of the skin may be stimulated by raising the 

 temperature of the surrounding air, while the whole body, with the 

 exception of the head, is enclosed in a convenient receptacle. 4 By 

 the hot-air method, Argutinsky 5 collected a quarter of a litre of sweat 

 in half an hour, at a temperature raised during the, experiment from 

 27 to 41 C. Schierbeck, 6 by the hygrometric method, calculated that 

 in his own case, when clothed and at rest, the air in contact with the 

 skin being at the normal temperature within clothing (32 C.), 2 or 3 

 litres of sweat were given off in twenty-four hours. No calculations of 

 the total secretion of sweat can be made from local estimates, because the 

 richness of various districts of the skin in sweat-glands is very different. 



In the body at rest the sweat is evaporated as fast as it is formed, 

 and it is only under conditions exciting the glands to increased action,, 

 that the fluid collects upon the surface. 



In the resting condition of the body the temperature of the 

 surrounding air must be raised to about 33 C. before the stimulus to 

 increased activity of the sweat-glands is evoked. 7 



The following table is of interest as indicating that, at the time of 



1 Weber, Arch. f. mikr. Anat., Bonn, 1888, Bd. xxxi. S. 499. For further information 

 on such glands, see Owen, ''Comparative Anatomy and Physiology of Vertebrata," London, 

 1868, vol. iii. p. 632 ; Leydig, Ztschr. f. wissensch. ZooL, Leipzig, 1850, Bd. ii. S. 1 (anal 

 glands). 



2 Anselmino, Wagner's " Handworterbuch d. Physiol.," art. "Haut." 



3 Schierbeck, Arch. f. PhysioL, Leipzig, 1893, S. 116. 



4 Favre, Compt. rend. Acad. d. sc., Paris, 1852, tome xxxv. p. 721. 



5 Arch.f. d. gcs. PhysioL, Bonn, 1890, Bd. xlvi. S. 594. 6 Loc. cit. 

 7 Schierbeck, 'loc. cit. 



