342 PULMONARY MUCOUS TISSUE. 



and functions are accompanied. These reactions are ex- 

 tremely complex; consisting of separations, fermentations, 

 etc. 



The attempt has, however, been made to determine more 

 exactly the seat of these combustions ; are they produced in 

 the histological elements themselves, or in the capillary 

 vessels which come in contact with these elements ? The 

 German physiologists, who have made a special study of this 

 question, are divided, in regard to it, into two schools. 1. 

 Ludwig and his followers maintain that the act of oxidation 

 and the production of carbonic acid take place in the interior 

 of the capillary vessels. The arguments adduced in favor of 

 this opinion rest chiefly on the recent analyses made by Ham- 

 marsten of the gases of the lymph : these show that this fluid 

 which carries off the disintegrated parts of the tissues, directly 

 contains a smaller quantity of carbonic acid than the venous 

 blood; whence they conclude that the carbonic acid is not 

 produced in the histological elements. 2. Pfliiger considers 

 that the tension of the carbonic acid in the lymph does not 

 give the exact measure of the tension of this gas in the histo- 

 logical elements themselves. In order to estimate this ten- 

 sion as directly as possible, Pfliiger has recourse to the normal 

 secretions of the economy (the urine, bile, saliva), which, 

 being the immediate result of the destruction of the cellular 

 elements, must represent exactly the amount of carbonic acid 

 which these contain. In all these secretory products the 

 tension of the carbonic acid is much greater than in the 

 venous blood. Pfliiger concludes from this, that carbonic 

 acid is formed in the tissues, and not in the blood, and that 

 the seat of the respiratory combustions is to be found in the 

 deeper tissues. 



The heat thus produced in all the different parts of the 

 organism, and more especially in some internal foci (the 

 liver) is equally distributed throughout the body by the cir- 

 culation of the blood ; the more vascular any part of the 

 body is, the more active is the circulation in it, and the more 

 nearly it approaches the maximum of its temperature : in 

 some parts (the choroid plexus, articulations, etc.) the vascu- 

 lar richness serves no other purpose than that of warming the 

 part (see Circulation and Vaso-motors). 



A loss of heat from the surface of the body takes place 

 when the environment is of lower temperature than that 

 of our bodies; the organism, however, possesses various 

 methods of mitigating the injurious effects produced by this 



