316 GENERAL REVIEW OP NUTRITIVE OPERATIONS. 



milk of the Human female ; and that of sugar in the milk of 

 the Mare. The milk of the Cow, if a portion of its casein 

 were removed, would resemble Human milk more nearly than 

 any other ; and it is therefore hest for the nourishment of 

 Infants, when the latter cannot be obtained. The important 

 influence of Mental emotion on this secretion has already been 

 noticed ( 353) ; and many more instances might be related, 

 were not the ordinary facts in regard to it generally known. 



CHAPTEE VIII. 



GENERAL REVIEW OF THE NUTRITIVE OPERATIONS FORMATION 

 OF THE TISSUES. 



General Review of the Nutritive Operations. 



378. IN the preceding Chapters (HI. to v.) those processes 

 have been described, by which the alimentary materials that 

 constitute the raw material of the tissues, are converted into 

 a fluid adapted for the Nutrition of the body ; and we then 

 (CHAPS, vi. and VH.) considered those functions, by which this 

 fluid is kept free from the impurities it acquires during its 

 circulation through the body, and is maintained in the state 

 which alone can adapt it to the purposes it is destined to fulfil. 

 These purposes may be regarded as fourfold. In the first 

 place, the Blood is destined to supply the materials of the 

 fabric of the body ; which, as it is continually undergoing 

 decay ( 68), requires the means of as constant a renovation. 

 Secondly, the Blood (in most animal& at least) serves to convey 

 to the tissues the supply of oxygen which is required by 

 them, especially by the muscular and nervous tissues, as a 

 necessary stimulus to the performance of their functions. 

 Thirdly, the Blood furnishes to the secreting organs the 

 materials for the elaboration of the various fluids, which have 

 special purposes to serve in the Animal economy, such, for 

 instance, as the Saliva, Gastric juice, Milk, &c. And lastly, 

 the Blood takes up, in the course of its circulation, the pro- 

 ducts of the waste or decomposition of the various tissues, 

 which it conveys to the several organs, the Lungs, Liver, 



