230 OF THE BLOOD GENERAL CONSIDERATIONS. 



larger proportion of colorless corpuscles iu the blood than at any subsequent 

 period, at least in the healthy state. Further, as Prof. J. H. Bennett has 

 pointed out, that peculiar condition of the blood, which consists iu the mul- 

 tiplication of its colorless corpuscles, is almost always associated with hyper- 

 trophy of one or other of these bodies ; and in one case of this kiud, in which 

 the Thyroid was the organ affected, its cells and their included nuclei were 

 observed to be considerably smaller than usual, and the same peculiarity 

 presented itself in the colorless corpuscles of the blood. 1 Hence there seems 

 a strong probability, that whilst the plasma of the blood is being elaborated 

 by these bodies, a constant supply of new blood-corpuscles is also afforded by 

 them ; 2 and that they thus effect for the nutrient materials directly absorbed 

 into the Sanguiferous system, that which the glandulse in connection with 

 the Absorbent system accomplish for the substances which it has taken up. 



CHAPTER VII. 



OF THE BLOOD ; ITS PHYSICAL CHARACTERS, ITS CHEMICAL 

 COMPOSITION, AND ITS VITAL PROPERTIES. 



1. General Considerations: Quantity of Blood. 



168. FROM the materials supplied in the Food, there is prepared, by the 

 Digestive and Assimilative processes described iu the preceding Chapters, 

 that general nutritive liquid, the Blood, which, in the organism of Man (as 

 in that of all the higher Animals) is constantly circulating through its ves- 

 sels during the whole of life. From this liquid, each portion of the solid 

 tissues has the power of extracting, and of appropriating to its own use, the 

 particular components of its substance ; these either .pre-existing as such in 

 the blood, or being capable of being readily formed from it by a process of 

 chemical transformation. During its circulation, moreover, the blood draws 

 into its current the effete particles which are set free by the disintegration of 

 the tissues (probably at the very time when it gives forth the components of 

 the newly forming structures), and conveys them to the various organs which 

 are provided for their elimination. Hence the Blood not only contains the 

 materials for the renovation of the tissues, but also the products of their de- 

 cay ; but there is an important difference in the proportion of these two sets 

 of components, for whilst the former make up the principal part of the mass 

 of the fluid, the latter are only detectable in it with difficulty, so long as the 

 excretory organs maintain their normal activity ; and only make their pres- 

 ence obvious, when they accumulate unduly, in consequence of the retarda- 

 tion or suspension of the eliminating operations. But besides thus meeting 

 the demand occasioned by the constructive operations, and preventing the 

 results of the destructive from exerting an injurious influence on the system, 

 the Blood acts (so to speak) as the carrier of Oxygen introduced from the 

 atmosphere, to the Muscular and Nervous tissues, to who^e peculiar vital 



1 This fact is the more weighty, as, in another case observed by Prof. Bennett, 

 tli^ colorless corpuscles of the blood were of two dhtinet sizes, the smaller corre- 

 sponding with the nuclei of the larger ones; and the lymphatic glands were found to 

 ) crowded with corpuscles also of two distinct size's, exactly corresponding with 

 those of the blood. (See Edin. Monthly Journal, Oetober, 18-31 ) 



2 This view has been ably supported by Prof. J. H. Bennett, in Edin. Monthly 

 Journ., March, 1852; and in his treatise on Leucocytluemia. 



