CHAP, in.] CUTANEOUS SECRETION. 387 



words, the frog is able to breathe without lungs, respiration being 

 carried on efficiently by means of the skin. In mammals and in 

 man this cutaneous respiration is, by reason of the thickness of the 

 epidermis, restricted to within very narrow limits; nevertheless, 

 when the body remains for some time in a closed chamber to 

 which the air passing in and out of the lungs has no access (as 

 when the body is enclosed in a large air-tight bag fitting tightly 

 round the neck, or where a tube in the trachea carries air to and 

 from the lungs of an animal placed in an air-tight box), it is found 

 that the air in the chamber loses oxygen and gains carbonic acid. 

 The amount of carbonic acid which is thus thrown off by the skin 

 of an average man in 24 hours amounts to about 10 grms., or accord- 

 ing to some observers to (no more than) about 4 grms., increasing 

 with a rise of temperature, and being very markedly augmented by 

 bodily exercise. It is stated that the amount of oxygen consumed 

 is about equal in volume to that of the carbonic acid given off, but 

 some observers make it rather less. It is evident that the loss 

 which the body suffers through the skin consists chiefly of water. 



When an animal, such as a rabbit, is covered over with an 

 impermeable varnish such as gelatine, so that all exit or entrance 

 of gases or liquids by the skin is prevented, death shortly ensues. 

 This result cannot be due, as was once thought, to arrest of 

 cutaneous respiration, seeing how insignificant is the gaseous inter- 

 change by the skin as compared with that by the lungs. Nor are 

 the symptoms those of asphyxia, but rather of some kind of 

 poisoning, marked by a very great fall of temperature, which 

 however does not seem to be the result of diminished production 

 of heat, since it is said to be coincident with an actual 

 increase of the discharge of heat from the surface. The 

 animal may be restored, or at all events its life may be prolonged 

 with abatement of the symptoms, if the great loss of heat which is 

 evidently taking place be prevented by covering the body thickly 

 with cotton wool, or keeping it in a warm atmosphere. The 

 symptoms have not as yet been clearly analysed, but they seem to 

 be due in part to a pyrexia or fever possibly caused by the reten- 

 tion within or re-absorption into the blood of some of the con- 

 stituents of the sweat, or by the products of some abnormal meta- 

 bolism, and in part to a dilation of the cutaneous vessels which 

 causes an abnormally large loss of heat, even through the varnish. 



The Secretion of Perspiration. 



The skin contains, besides the ordinary sudoriparous glands, the 

 sebaceous glands, and the special odoriferous glands of the axilla, 

 anus, and other regions. With regard to the various volatile and 

 odoriferous substances peculiar to sweat, and especially with regard 



252 



