MAKUAL OF CATTLE-EEEDIKa. 83 



gas from the blood is made incomplete or suspended en- 

 tirely, and substantially the same resulte ensue, though 

 more slowly. 



Respiration through the Skim — In addition to the 

 exchange of gases between the air and the blood which 

 goes on in the lungs, a similar process takes place, though 

 to a smaller extent, through the skin. 



The true skin, underlying the cuticle or scarf-skin, is 

 penetrated by capillary blood-vessels, and in its passage 

 through these capillaries the blood gives off some carbonic 

 acid and takes up some oxygen by diffusion through the 

 skin. The amounts thus given off and taken up .are small 

 compared with the corresponding amounts in the lungs, 

 but they are still not inconsiderable. The skin likewise 

 acts, by means of its sweat-glands, as a chaimel for the re- 

 moval of water from the system. Large amounte of water 

 are continually evaporating from the skin in the form of 

 the " insensible perspiration," while under certain circxmi- 

 stances the excretion of water is so rapid as to give rise to 

 the formation of visible drops- 



The distribution of oxygen through the body is 

 accomplished by means of the circulation. Each little cor- 

 puscle carries its load of oxygen from the lungs through 

 the heart and arteries into the capillaries. 



There, as we have seen, the substances formed in the 

 minute cells of the tissue by the decomposition of their 

 contents under the influence of the vital force, diffuse 

 into tlie blood, and hei^e they meet the oxygen con- 

 tained in the corpuscles and unite with it — are burned, 

 producing the animal heat Innumerable intermediate 

 products are formed in this process, but the final result 

 is in all cases the same. All the non-nitrogenous sub- 

 stances yield carbonic acid and water; the nitrogenous 



