264 HALOIDS AND HALOID BASES. 



quite recovered its normal character ; hence we frequently observe 

 a very abundant deposition of fat after typhus and other diseases 

 resulting in ansemia. We shall enter more fully into the consider- 

 ation of this subject, when we proceed, at the close of the phy- 

 siological chemistry, to treat of the general phenomena of nutrition. 

 We now enter upon what may be termed the physico-physi- 

 ological uses of fats. Liebig has shown; with his characteristic 

 ingenuity, that the fats mainly contribute to the excitement and 

 maintenance of animal heat. One of the most ingenious of 

 Liebig^s deductions is his classification of the elements of nutrition 

 into true plastic nutrient substances and food for the respiration, 

 to the latter of which he especially ascribes the functions of main- 

 taining animal heat. But as, in our observations on the processes 

 of respiration and nutrition (in the third volume), we shall enter 

 more fully into the examination of Liebig's views on this subject, 

 we shall here only observe that, however paradoxical and apodictic 

 many of his deductions may appear, he has founded a new era in 

 physiological chemistry, and has been the means of throwing a 

 clearer light over the whole economy of the organism. Owing to 

 his aphoristic mode of representation, his views have often been 

 misunderstood and erroneously interpreted, and many persons 

 have even supposed that they must assume that fat is simply 

 transferred into the blood, where it is burned like the oil in a lamp, 

 or the coke in a steam-engine. A more attentive examination of 

 Liebig's writings shows, however, that he did not entertain so 

 crude a view of the subject. But we must admit that we do not 

 consider as wholly groundless the objection which has been 

 advanced against Liebig, that he regards animal heat as too inde- 

 pendent of other processes. Animal heat can only be considered 

 under one of two points of view ; that of being an incidental 

 phenomenon and the mere result of certain vital processes, or as 

 being necessary to the maintenance of definite animal processes and 

 functions. If the latter view be even partially correct, we must recol- 

 lect that animal life is not generally dependent upon a definite high 

 temperature, and that numerous cold-blooded vertebrate animals 

 perform the processes of digestion, respiration, blood-formation, and 

 of the nervous system, as well at a low temperature, as warm-blooded 

 animals do at 37*5. If, on the other hand, animal heat were a 

 mere incidental phenomenon, the fats would appear to be most 

 uselessly expended in serving no other purpose than that of deve- 

 loping heat. The fat of the living body therefore probably conduces 

 to other ends in the animal economy. 



