THE BLOOD. 47 



therefore, the colourless blood corpuscles be termed " parent 

 cells," they must be considered as pregnant with the embryo 

 materials of the tissues and secretions, and not with " young 

 blood cells." 



It is scarcely necessary to observe that these highly in- 

 genious views of Mr. Addison are by no means established. 

 That the cells of glands and their contained granules are inti- 

 mately connected with secretion there are many facts to prove ; 

 but that the white corpuscles of the blood are, in the animal 

 economy, the special organs of secretion, and also that the 

 secretions said to be elaborated by them, escape from them, 

 not by transudation through their membranes, but are set free 

 by the entire and final dissolution of the corpuscles, are 

 views which cannot be safely adopted until much additional 

 evidence is adduced in support of them. 



The opinion entertained by Dr. Barry, that the colourless 

 corpuscles are " parent cells," seems to me to be purely 

 hypothetical. 



Let us now bestow a few reflections upon Nutrition. 



Uses in connexion with Nutrition. That the white cor- 

 puscles are concerned in the process of nutrition, there 

 is more evidence to show than there is in favour of their 

 connexion with that of secretion. The question to be 

 solved, however, is, in what way do these corpuscles ad- 

 minister to nutrition? do they contribute to nutrition 

 and growth, by their direct apposition to and incorporation 

 with the different tissues of organs ? This is the opinion of 

 Mr. Addison, who says of them, that they are the " founda- 

 tions of the tissues and the special secreting cells, the link 

 between the blood and the more solid structures, the unity 

 from which the pluralities arise." 



Dr. Martin Barry also adopts the notion that tissues are 

 formed by the direct apposition of the blood corpuscles. Dr. 

 Barry makes no exact distinction between the red and the 

 colourless globules ; but from the fact of his calling the latter 

 " parent cells " filled with " young blood discs," it would 

 appear that he considered that the red corpuscles gave origin to 

 the different structures of the body by their direct union and 



