256 



HITCHCOCK'S ANATOMY 



largely contained in vegetable food very closely resembles 

 fibrin (which is the form that the nutrient portion of the food 

 must be in before it can nourish the greater part of the body, 

 and especially the muscles), still chemical analysis shows that 

 the gluten must receive another equivalent of oxygen before 

 it is fitted to reproduce the different tissues of the body. And 

 the only way in which this oxygen can be given to the body 

 is either through the lung;s or skin. 



454. Amount of Air which the Lungs can Contain — 

 The amount of air which the lungs actually do contain is by 

 no means the amount that should be actually supplied to them. 

 For the air which surrounds the body is very rarely indeed 

 perfectly pure, but is contaminated with the previously ex- 

 haled breath, on account of the law of diffusion of gases, 

 which is, that when two gases are brought into contact they 

 immediately commingle with each other. Experiment shows 

 that between 350 and 400 cubic feet of air are actually ex- 

 haled during the twen'y-four hours ; but experience shows 

 that the least quantity which should be allowed for dwelling- 

 houses, shops, and school-bouses, should be 800 feet in order 

 to furnish a sufficient supply of oxygen. 



CALORIFIC ORGANS. 



455. Heat-producing Organs — Theory of Animal Heat. 



— The organs which produce animal heat are essentially those 

 employed in the act of breathing and the circulation of the 

 blood, and consequently already explained, but the actual 

 m 3thod by which it is produced has for a long time perplexed 

 physiologists. The theory which now is most readily accepted 

 makes the function to be a chemico-vital one, or a chemical 



What is that element which principally nourishes the muscles? 454. What is the law 

 of diffusion of gases, and what modifying influence does this have on the hygiene of res- 

 piration ? How many cuhic feet of air should be allowed to every in-door laborer or 

 student? 455. What are the heat-producing organs? What is at present the most 

 readily accepted theory of animal heat ? 



