THE BLOOD. 45 



USES OF THE WHITE CORPUSCLES. 



The uses of the white corpuscles have not as yet been 

 fully determined ; enough, however, of their nature has 

 been ascertained to show that they are closely connected 

 with the functions of Nutrition and Secretion. We shall 

 here invert the natural order in which the description of 

 these subjects should be entered upon, and speak first of 

 secretion. 



Uses in connexion with Secretion. It would appear that, 

 for the most part, secretions are formed in cells : the cor- 

 rectness of this statement is, in some degree, proved by the 

 fact that the lower classes of the vegetable kingdom are 

 entirely constituted of cellular tissue. 



It is also further supported by the fact, that the essential 

 structure of all glands in the animal frame is that of cells. 



It would appear, also, that the cells, entering into the 

 composition of a single organ, have the power of producing 

 more than one kind of secretion. This is witnessed in the 

 petals of many flowers, the cells of which frequently elaborate 

 fluids of several distinct colours. 



There is much reason to believe, that the granules, which 

 are so constantly associated with the cells, are the active 

 agents engaged in the production of the secretion, the exact 

 constitution of these granules determining the character of 

 the secreted product. 



Now, in the white corpuscles of the blood we have precisely 

 the same granular constitution which is seen to belong to 

 cells which are indisputably engaged in the process of secre- 

 tion. 



From the observation of these and other facts Mr. Addison 

 has been led to entertain the opinion, that the white corpuscles 

 of the blood " are very highly organised cells, from which the 

 special tissues and the secretions are elaborated." * In continu- 

 ation of this subject, Mr. Addison goes on to remark, " And 



* Experimental Researches, Transactions of Prov. Med. and Surg. 

 Association, vol. xii. p. 260. 



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