438 LECTURE XVIII. 



ture. If this increase in temperature be prevented, the animal will not 

 die. 1 



We recognize certain kinds of fish, especially the loach ;< Cobitis fossilis, 

 in which there is a peculiar intestinal respiration. The middle intestine 

 of the Cobitis contains an abundant supply of capillary blood-vessels and a 

 peculiarly transformed epithelium. These fish swallow air, and discharge 

 gases through the rectum. The gas which leaves the body contains less 

 oxygen and more carbon dioxide than that entering. 2 



With the remaining members of the animal kingdom, the intestine plays 

 no part in the gas-exchange. To be sure, the alimentary canal contains 

 gas, resulting, in part, from swallowed air, which with the food, the saliva, 

 and drink, is constantly being introduced, and largely from bacterial 

 decomposition, fermentation, etc. Furthermore, carbonic acid is set free 

 in the neutralization of the carbonates of sodium in the intestinal secretions 

 by the hydrochloric acid from the stomach. The oxygen of the swallowed 

 air is taken up little by little by the intestinal walls; and similarly, on 

 account of its partial pressure, the carbon dioxide diffuses to some extent 

 into the intestinal walls and into the blood-vessels, and in other cases 

 these gases are given up from the vascular system, if the amount present 

 in the intestine is slight. Likewise other gases, such as hydrogen, methane, 

 sulphureted hydrogen, and nitrogen, are absorbed according to the laws 

 of gas absorption, and can be eliminated by the lungs. 



1 Cf. Laschkewitsch : Arch. Anat. Physiol. 1868, 61. R. Winternitz: Arch, exper. 

 Path. Pharm. 33, 286 (1895). E. Babak: Pfliiger's Arch. 108, 389 (1905). 



2 Baumert: Chemische Untersuchungen der Respiration des Schlammenpeizgers, 

 Breslau, 1855. D. Calugareanu: Pfluger's Arch. 118, 42; 120, 425 (1907). 



