130 HEALTH AND DISEASE 



emulsified as it should have been, for the reason, as it was afterwards ascer- 

 tained, that the water was extremely hard. The addition of some washing- 

 soda to the water had the effect of producing a perfect emulsion, and the 

 process of dipping the flock was continued without any further disaster. 



It had previously been known that the poisonous action of carbolic 

 acid was especially marked when the agent was applied to the skin, and 

 the explanation ordinarily given was, that it acted as a powerful depressor 

 of nerve function. It must, however, be allowed that it could not possibly 

 act upon the nerves without being absorbed in the first place through the 

 cuticle, beneath which the nerves terminate on the surface of the true skin. 



The absorption of fatty material by the skin probably largely depends 

 on the affinity which it has with the sebaceous secretion, enabling it to 

 pass into the follicles, and there certainly appears to be good reason to 

 suppose that some of the nutritive constituents of milk are thus taken 

 into the system, especially the fatty matters, as young children when 

 incapable of taking nourishment by the mouth have been sustained for 

 some time by being kept for considerable periods in baths of warm milk. 



Skin as an Organ of Secretion. — Whatever importance may be 

 attached to skin as an organ of absorption, its activity as a secreting 

 organ is altogether beyond question. In the first place, the cuticular 

 cells are constantly being thrown off under the influence of attrition, and 

 the vascular surftice of the true skin is actively engaged in furnishing 

 material for the reproduction of new cells. Further, the sudoriparous 

 and sebiparous glands discharge both fluid and solid substances, in the 

 form of secretions, which, as will presently be seen, perform important 

 functions. As has already been stated, the sudoriparous or sweat glands, 

 which are extremely numerous, separate a fluid from the blood, a con- 

 siderable quantity of which is constantly being given off as invisible 

 vapour, or insensible persj)iration; while under conditions which excite 

 the circulation and still further increase the body temperature, a large 

 quantity of liquid is poured out, carrying with it a considerable amount 

 of solid material, in which is contained various salts of the blood, as well 

 as a large number of acids, including butyric, formic, propionic, and an 

 acid peculiar to the sweat, which is called sudoric. This fluid perspiration 

 is distinguished as sensible jyerspiration. The reaction of the sweat is 

 generally acid. From some parts, perspiration contains a larger proportion 

 of fat than from others, in association with certain nitrogenous matters, 

 urea among them. It is understood by physiologists that the nervous 

 system has considerable influence in regulating the function of perspiration. 



One very important purpose which the perspiration serves, is that of 

 lowering the temperature of the body by evaporation, and another is the 



