SECRETION. 315 



these obscure processes by the discoveries of Schlei- 

 den and Schwann, relative to the modes of organic 

 developement :* for it is probable that the mode in 

 which the losses of substance in the organs are 

 repaired is similar to that in which those organs 

 were originally formed, and their growth effected. 

 This latter process is now known to consist in 

 the successive evolution of vesicles, or cells, from 

 certain primitive nuclei : and it is probable that 

 the corpuscles with which the blood abounds con- 

 stitute the nuclei from which the nascent organiza- 

 tion takes its rise. Dr. Barry has found that these 

 corpuscles, when effused from the blood-vessels, 

 spontaneously undergo rapid and incessant changes 

 of form, during a certain period; and that they 

 ultimately assume the appearance of cells, which, 

 in the progress of their further developement, ac- 

 quire different characters according to the parti- 

 cular nature of the elementary texture they are 

 destined to compose, whether it be cellular, mus- 

 cular, or nervous.! Valentin has traced the forma- 



* See Vol. I. p. 56, and 86, notes. 



t An account of these observations was given in a paper lately 

 read at the Royal Society, (June 4th, 1840), and of which an 

 account will shortly appear in its proceedings. In another paper 

 read to the same Society, on the 18th of June, Mr. Bowman has 

 shown that the primitive fibres, or fasciculi, as he terms them, of the 

 muscles of voluntary motion, are composed of fibrils, (Jibrillce)^ 

 marked by alternate dark and light points, sometimes resembling a 

 string of beads, and presenting, by the apposition of the fibrils com- 

 posing a fasciculus, the appearance of those transverse striae which 

 have been often noticed in the microscopical examination of the 

 muscular structure. In these, as well as in other organic structures, 

 he has traced the presence of numerous minute corpuscles, being 

 apparently the nuclei of the cells from which the developement of 

 the fibres had originated. 



