270 BLOOD. 



We have no intention of asserting that such experiments as 

 these possess extreme accuracy, but they appear to us to have the 

 advantage of giving in this manner the minimum of the blood con- 

 tained in the body of an adult man ; for although some solid 

 substances, not belonging to the blood, may be taken up by the 

 water from the parenchyma of the organs permeated with capillary 

 vessels, the excess thus obtained is so completely counteracted by 

 the deficiency caused by the retention of some blood in the capil- 

 laries, and in part by transudation, that our estimate of the quantity 

 of blood contained in the human body may certainly be considered 

 as slightly below the actual quantity. 



It is by no means decided whether fat men and animals contain 

 less blood than lean ones, notwithstanding the experiments of 

 Schultz* on fat and lean oxen (in the latter, he found an excess of 

 20 or 30 pounds of blood). When we enter upon the considera- 

 tion of the animal processes, and especially the metamorphosis of 

 matter, we shall treat in detail of the sources from which the blood 

 flows, its progressive and regressive formation, both in relation 

 to its individual constituents and collectively, and of its general 

 physiological import ; for the blood is the centre round which the 

 general metamorphosis of animal matter revolves, and in which it 

 is perfected. As we have already considered the origin and meta- 

 morphosis of the chemical constituents of the blood, in the first 

 volume, it only remains for us here briefly to notice the mode of 

 development and the destination of its morphological elements, 

 although these questions may be regarded as belonging more 

 especially to histological physiology. 



The investigations of the most distinguished physiologists of 

 the present day render it highly probable that there is more than 

 one seat of formation of the colourless blood-cells. They are, un- 

 doubtedly, for the most part, formed in the chyle, and they are 

 likewise produced, as has been before observed, in the liver ; at all 

 events, under certain conditions : but their formation, or at all events 

 their development and growth, are not confined to any one definite 

 locality, but proceed in the vessels of very different organs. H. 

 Miillerf and Kb'lliker J have recently devoted special attention to the 

 development of the colourless blood-cells in the chyle, a subject 

 that had already been very fully considered by several earlier 

 observers, especially J. Muller, E. H. Weber, Schwann, Henle, and 



* System der Circulation. Stuttgart, 1836. 

 t Zeitschr. f. rat. Med. Bd. 3, S. 204278, 

 J Ibid. Vol. 4, pp. 142144. 



