HEAT OF ANIMALS AND PLANTS. 425 



Carbonic acid, but other products of the changes in composition which 

 the food undergoes when introduced into the system. 



758. The same remarks apply, and with yet greater force, to the 

 Intestinal glandulae ; whose function it is, not merely to remove the 

 putrescent matter ordinarily formed by the disintegration of the tis- 

 sues, or by the decomposition of unassimilated food, but also to draw 

 off the still more offensive products of such changes as take place in 

 disease. Thus there are conditions of the system, in which, without 

 any well-marked disorder, the faeces emit a peculiarly foetid odour ; 

 and with these is almost always associated a depressed state of mind. 

 Now it can scarcely be doubted, that the real fault is here rather in 

 the early part of the nutritive operations, than in the excretory func- 

 tion ; and that the fcetor of the contents of the intestine depends upon 

 the undue formation of putrescent matter in the system, which, by taint- 

 ing the blood, causes its action upon the brain to become unhealthy. 

 The object of the physician will be here to eliminate the morbid 

 product, by the moderate use of purgatives ; and so to regulate the diet 

 and regimen, as to correct the tendency to its formation. An exces- 

 sive foetor in the evacuations, as well as in the exhalations from the 

 skin and lungs, is peculiarly characteristic of those very severe forms 

 of typhus (now, happily, of comparatively rare occurrence), which are 

 termed putrid fevers. Here the whole of the solids and fluids of the 

 body appear to have an unusual tendency to decomposition, in conse- 

 quence of the introduction of some morbid agent, which acts as a fer- 

 ment ; and the system attempts to free itself from the products of that 

 decomposition, by the various organs of excretion, particularly the Skin 

 and Intestinal surface. 



759. It is of great importance that the Student should form clear 

 conceptions on this subject ; and that he should not (as too often hap- 

 pens), by directing his remedies to the mere symptoms or results of a 

 disease, act in precise opposition to the natural tendency of the system 

 to free itself from some unusual noxious matter, through those channels 

 which are ordinarily destined to carry off only the regular products of 

 its disintegration. 



CHAPTER X. 



OF THE DEVELOPMENT OF HEAT, LIGHT, AND ELECTRICITY, IN THE 



ANIMAL BODY. 



760. IT has been shown, in an earlier part of this volume (CHAP, n.), 

 that all Vital actions require a certain amount of Heat for their per- 

 formance ; and that there is a great variety amongst the different 

 classes of Animals, both in regard to the degree of Heat which is most 

 favourable to the several processes of their economy, and in regard to 

 their own power of sustaining it, independently of oscillations in the 



