430 NUTRITION. 



living animal and placed in an atmosphere of hydrogen or 

 nitrogen. 



Experiments on the influence of the sympathetic nerves 

 upon the temperature of particular parts have completed the 

 chain of evidence in favor of the localization of the heat- 

 producing function in the tissues. It is not our purpose to 

 discuss the relations of the sympathetic system to nutrition, 

 deferring this subject until we come to treat specially of the 

 nervous system ; but the facts bearing on calorification are 

 briefly as follows : 



If the sympathetic nerve be divided in the neck of a 

 rabbit, or any other warm-blooded animal, the side of the 

 head supplied by this nerve will become from flve to eight 

 or ten degrees warmer than the opposite side, or than the 

 rest of the body. This observation we have repeatedly veri- 

 fied. The conditions under which this local exaggeration of 

 the animal heat is manifested are, dilatation of the arteries 

 of supply of the part,- so that it receives very much more blood 

 than before, and increased activity of the general process of 

 nutrition. It also has been observed, in experiments upon the 

 horse, that the blood coming from the part is red, and con- 

 tains very much more oxygen than ordinary venous blood. 1 



The recent observations of MM. Estor and Saint-Pierre 

 show that the blood coming from inflamed parts, in which 

 there is a considerable elevation above the normal temper- 

 ature, is red, and contains from fifty to two hundred and 

 fifty per cent, more oxygen than ordinary venous blood. 2 

 These facts are regarded as inconsistent with the view that 

 the temperature of parts is due chiefly to oxidation; but 

 when we consider the fact that, in the conditions above 

 mentioned, the actual quantity of blood circulating in these 



1 BERNARD, Sur la quantite d'oxygene que contient le sang veneux dcs organes 

 glandulaires, d Petal def auction et d Tetat de repos. Comptes rendus, Paris, 1858, 

 tome xlvii., p. 398, note. 



2 ESTOR ET SAINT-PIERRE, Recherches experimentales sur les causes de la colora- 

 tion rouge des tissus enflammes. Journal de Panatomie, Paris, 1864, tome i., p. 

 412, and Du siege dcs combustions respiratoires. Ibid., 1865, tome ii., p. 314. 



