CHAP, in.] ELIMINATION OF WASTE PRODUCTS. 697 



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 may be doubted, however, whether the 

 carbonic acid comes direct from the blood ; it may come from de- 

 compositions taking place in the sweat, of carbonates for instance. 

 Similarly the oxygen which disappears may be simply used in 

 oxidizing some of the constituents of the sweat. It is evident 

 that the loss which the body suffers through the skin consists, 

 besides a small quantity of sodium chloride, chiefly of water. 



When an animal, a rabbit for instance, 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 and doubtful is the 

 gaseous interchange by the skin as compared with that by the 

 lungs. Nor are the symptoms at all those of asphyxia, but rather 

 of some kind of poisoning, marked by a very great fall of 

 temperature, which however seems to be the result not of 

 diminished production of heat, but of an 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 retention within or re- 

 absorption into the blood of some of the constituents of the sweat, 

 or by the products of some abnormal metabolism, and in part 

 to a dilation of the cutaneous vessels caused by the application of 

 varnish ; owing to the dilated condition of the cutaneous vessels 

 the loss of heat through the skin is abnormally large, even though 

 the varnish may not be a good conductor. 



440. Absorption by the skin. Although under normal circum- 

 stances' the skin serves only as a channel of loss to the body, it has 

 been maintained that it may, under particular circumstances, be a 

 means of gain ; and the little which we have to say on this matter 

 may perhaps be said here. Cases are on record where bodies are 

 said to have gained in weight by immersion in a bath, or by 

 exposure to a moist atmosphere during a given period, in which 

 no food or drink was taken, or to have gained more than the 

 weight of the food or drink taken; the gain in such cases must 

 have been due to the absorption of water by the skin. Direct 

 experiments, however, throw doubt on these statements, for they 

 shew that under ordinary circumstances such a gain by the skin is 

 slight, being apparently due to mere imbibition of water by the 

 upper layers of the epidermis. 



Absorption of various substances takes place very readily by 

 abraded surfaces where the dermis is laid bare or covered only by 



