Chap, hi.] ELIMINATION OF WASTE PRODUCTS. 553 



sumecl 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 decompositions taking place in 

 the sweat, of carbonates for instance. Similarly the oxygen 

 which disappears may be simply used in oxydizing 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 gelatin, 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 insig- 

 nificant 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. 

 Owing to the dilated condition of the cutaneous vessels, caused 

 by the application of varnish, the loss of heat through the skin 

 is abnormally large, even though the varnish may not be a good 

 conductor. 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 analyzed, but they seem to be due in part to a pyrexia 

 or fever possibly caused by the retention within or reabsorp- 

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

 or by the products of some abnormal metabolism. 



§ 352. Absorption by the skin. Although under normal 

 circumstances the skin serves only as a channel of loss to the 

 body, it has been maintained that it may, under particular cir- 

 cumstances, 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, how- 

 ever, 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 



