130 RESPIRATION 



face. Scharling, Rohrig, and others proved that carbon dioxide was 

 given off from all parts of the body, but at very various rates in different 

 portions. Anything which increases the vascularity of the skin increases 

 also the respiration through it. As in case of the pulmonary interchange, 

 heightened metabolism causes a livelier respiration through the skin; 

 so, according to Fubini and Rouchi, do food and light. In general, 

 cutaneous respiration seems to be about -g-J-g- (0.5 per cent.) of the pul- 

 monary respiration in quantity. Trial demonstrates that the human 

 skin will absorb, besides oxygen and carbon dioxide, carbon monoxide, 

 sulphuretted hydrogen, and the vapors of chloroform and of ether. 



In amphibians, dermal respiration, especially the absorption of oxygen, 

 is a much more important process than in mammals. Frogs, for example, 

 during a third or more of the year in temperate climates, are buried in 

 the mud at the bottom of ponds and streams, and the use of their lungs 

 must, then, for mechanical reasons be only nominal. But metabolism 

 goes on during these months and requires oxygen as it does in the summer 

 time. The carbon dioxide produced must be given off too, or the ani- 

 mal would soon die of asphyxia. Klug found that the body-surface of 

 the frog exclusive of the head excreted three or four times as much carbon 

 dioxide as did the lungs and the skin of the head namely, about 0.2 gm. 

 in the three hours of the experiment. In the summer the opposite ratio 

 obtains, the lungs then being the more important. Dissard, however, 

 proved that the frog dies when either of these respiratory organs (the 

 skin or the lungs) are thrown out of function. There is need, then, of 

 experiment in this direction on various classes of hibernating animals as 

 well as on the fakirs of India, who seem to be practically hibernating 

 men, their hearts and lungs being nearly at a standstill. 



Respiration through the Wall of the Alimentary Canal. Just as gases 

 pass outward through the skin from the underlying tissues, so a similar 

 and more varied respiratory interchange takes place into and out of the 

 alimentary canal. Ruge found carbon dioxide, hydrogen, nitrogen, 

 methane, and hydrogen sulphide in the rectum of a man, but no oxygen. 

 The carbon dioxide, methane, and hydrogen sulphide were most abun- 

 dant on a vegetable diet, the nitrogen on an animal diet, and the hydro- 

 gen on a milk diet. The proportion of carbon dioxide in the intestines 

 varies from 20 to 90 per cent, of the total gas content (Tappeiner). Its 

 partial pressure would be greater than that of the tissues, whether solid 

 or liquid, about the gut. The carbon dioxide of the intestines, therefore, 

 would soon make its way into the circulation and be excreted by way of 

 the lungs. 



Oxygen is promptly absorbed from the alimentary canal by the sur- 

 rounding tissues and largely by the capillary blood. It can seldom 

 be found below the duodenum, for most of it is absorbed by the wall of 

 the stomach. Pembrey relates that swimmers who are in the habit of 

 staying under water an exceptionally long time swallow air into their 

 stomachs, in order that the oxygen so taken in may be utilized as well 

 as that of the lungs. A kitten with clamped trachea will die in thirteen 



