CARE OF THE SKIN. 



419 



is very sensitive, and gives knowledge of the consistency of objects, 

 also whether they are rough or smooth, sharp or dull, etc. This 

 subject of general sensibility will be fully discussed in connection 

 with the Nervous Functions. 



(4) Respiration. Interchanges are constantly' taking place in 

 the skin analogous to those which take place in the lungs, although 

 to a much less extent. Oxygen is absorbed from the air by the 

 blood in the cutaneous blood-vessels, and at the same time carbon 

 dioxid is given off. In frogs these interchanges are much more 

 extensive than in man. 





FIG. 237. a, A vascular papilla ; b, a nervous papilla ; c, a blood-vessel ; d, a nerve- 

 fiber; e, a tactile corpuscle (after Biesiadecki). 



(5) Regulation of temperature, which has already been dis- 

 cussed (page 415). 



Care of the Skin. That the skin may perform its functions 

 properly it must be taken care of. The orifices of the ducts of 

 the perspiratory and sebaceous glands must be kept free, so that 

 they may not become clogged. If the skin of an animal is 

 covered with varnish, it speedily dies. This is not due to the 

 retention of waste-materials, which act as poisons, but to the great 

 loss of heat, in the rabbit the temperature falling to 20 C. Ex- 

 periment has shown that if an animal that has been varnished is 

 packed in cotton and kept in a temperature of 30 C., it will 

 survive. 



Gerlach covered a horse and a rabbit with linseed oil, with the 

 following results : 



