80 ORGANISED FLUIDS. 



ceived should be the elaboration of the blood corpuscles ; and 

 some of them, as He \vson and Donne, not knowing well 

 what office ought to be assigned to that much discussed 

 organ, the spleen, have on various grounds considered it to 

 be the laboratory in which the work of development is carried 

 on. Of the dissolution of the red blood discs no definite or 

 decided observations hitherto *appear to have been made by 

 any observer. 



Observation has convinced me that the development of 

 blood corpuscles is not assigned to any particular organ of 

 the body, but that it occurs within the blood-vessels during 

 the whole course of the circulation and of life. During the 

 first formation of the blood in early embryonic life, the 

 corpuscles are said to be formed in the cells, which by their 

 union with each other give origin to the capillary vessels. 



Further, it is probable, that, while it is in arterial blood 

 that the work of development of blood corpuscles is most 

 active, it is in the venous fluid that the converse work of 

 dissolution is mainly effected. 



The development of blood corpuscles is also most active in 

 very early life, when growth is rapid, and it is likewise 

 more active than ordinary in adult existence, after haemor- 

 rhages, and in persons of the plethoric diathesis. In like 

 manner it may be presumed that the dissolution of red blood 

 corpuscles proceeds more quickly in anaemic conditions of the 

 system, and' in old age, while at the same time, at the latter 

 period, development of new corpuscles is more tardy. 



It is now hoped that a more satisfactory explanation of 

 the origin and end of the red blood disc has been given than 

 it was feared, when the writer first approached the considera- 

 tion of these difficult, though most important, questions, it 

 would have been in his power to have afforded. 



VENOUS AND ARTERIAL BLOOD. 



Venous and arterial blood differ in certain important re- 

 spects from each other ; arterial blood is of a brighter colour, 



