PROPERTIES OF THE BLOOD. 435 



application of an irritant. Hence the idea naturally arises, that (to use the 

 words of Mr. Wharton Jones) "there is some reciprocal relation between the 

 colourless corpuscles, and the parts outside the vessels, in the process of 

 nutrition." What that relation is, we shall now proceed to inquire. 



578. In regard to the purpose of the colourless corpuscles in the animal 

 economy, a view has been brought forward by the Author,* which increased 

 consideration has only served to strengthen ; and which he advances here with 

 some degree of confidence that it will be found, on attentive examination, war- 

 ranted by a large number of physiological analogies, though not capable of 

 being directly proved. That it may be rightly understood, a general sketch 

 of certain known operations of cells in Plants and Animals will be first given. 

 It is not difficult, on taking a comprehensive survey of the assimilating pro- 

 cesses, to find a number of examples in which cells are developed in a tempo- 

 rary manner ; growing, arriving at maturity, and then disappearing, apparently 

 without having performed any particular function. In the albumen of the 

 seed, for instance, this often takes place to a remarkable extent. In the Yolk 

 of the Egg there is a similar transitory development of cells, of which several 

 generations succeed each other, without any permanent structure being the 

 result. In the Germinal Vesicle, again (according to Dr. Barryt), several annuli 

 of cells are seen to occupy its cavity, when it is prepared for fecundation; and 

 the oldest and largest of these contain another generation : yet all these dis- 

 appear by liquefaction, as soon as the two permanent cells begin to be developed 

 in the centre ( 746). Further, in the subsequent development of all the cells 

 which are descended from these, and form the " mulberry mass," the same 

 process is repeated ; a great number of temporary cells being produced, only 

 to liquefy again as soon as the two permanent central cells make their appear- 

 ance. It can scarcely be imagined by the well-judging physiologist, that all 

 this cell-life comes into existence without some decided purpose ; and if we 

 can assign to it an object, the fulfilment of which is consistent with the facts 

 supplied by analogy elsewhere, this may be reasonably considered as having 

 a fair claim to be received as a physiological induction. In all these instances, 

 and in many more which might be quoted, the crude alimentary materials are 

 being prepared to undergo conversion into permanent and regularly-organized 

 structures. The very first union of the inorganic elements into the simplest 

 proximate principles, is effected by the cell-life of plants. The change of 

 these principles into the peculiar compounds which form the characteristic 

 secretions of plants, is another result of their cell-life. And there seems equal 

 ground for the belief, that the change of these proximate principles into the 

 peculiar glutinous sap, which is found wherever a formation of new tissue is 

 taking place, is equally dependent upon the agency of cells. Thus, the starchy 

 fluid which is contained in the ovule, previously to its fecundation, is probably 

 not in the state in which it can be immediately rendered subservient to the 

 nutrition of the embryo ; and the development of successive generations of 

 cells, which exert upon it their vitalizing influence, may be reasonably regarded 

 as the means by which the requisite change is effected. Exactly the same 

 may be said of the albuminous matter contained in the yolk of the egg, which 

 is certainly not in a condition in which it can be immediately applied to the 

 purposes of nutrition ; and its conversion may be regarded as commencing 

 with the development of transitory cells within its own substance, and as being 

 completed by means of the cells forming the inner layer of the germinal mem- 

 brane, by which it is subsequently taken up and introduced into the current of 



* Report on Cells, in British and Foreign Medical Review, Jan., 1843. 

 f Euibryological Researches. Third Series. 



