DR. MARTIN BARRY ON THE CORPUSCLES OF THE BLOOD. 235 



presented by the corpuscle or disc, — its passage into layers of discs, — the comparative 

 age of these, — the reappearance of red colouring matter, — and the secondary nature 

 of the "cell," than the figure now before us — fig. 133. To the description of this 

 figure, in connection with that of fig. 134, I particularly refer. 



159. Very much the same general remarks apply also to the elements of the 

 medullary portion of the brain (fig. 134.). 



The Elements of Muscular Tissue compared with Corpuscles of the Blood, 



160. Some of the earliest appearances presented by muscle, in its formation out 

 of blood-corpuscles, were given in one of my former communications to the Society -f-. 

 The muscles then examined, being involuntary, did not afford so interesting a field 

 for observation, as those the development of which has since had my attention, — the 

 voluntary muscles ; nor did I then prosecute the investigation farther than as oppor- 

 tunity was incidentally afforded. Nevertheless, it will be seen that the facts I have 

 now to mention, accord with those stated in that memoir. 



161. Corpuscles more or less blood-red, and having the appearance of young 

 blood-corpuscles, apply themselves to one another in the manner represented in 

 fig. 135, and also in the memoir just referred to; by which a necklace-like object 

 is produced. These corpuscles are cells, which I have found filled with discs (|3). 

 The appearance of these discs, together with that of the nucleus and nucleolus, re- 

 sembled in a remarkable manner the corresponding parts in certain states of the 

 germinal vesicle and germinal spot J. In no instance have I more clearly seen the 

 nature of the so-called " nucleolus" of authors ; and that at this part there exists an 

 orifice, communicating with the exterior of the cell (fig. 135. ^). By degrees, the 

 appearance of a cylinder is produced (fig. 136.), which becomes more perfect, as the 

 partitions between the cells, just mentioned, disappear — fig. 137. In this figure, nuclei 

 are still seen, having a parietal situation ; these being, as Schwann supposed, the 

 nuclei of the original cells (fig. 135.). It must not, however, be supposed that no 

 change takes place in the nuclei ; or that the nuclei seen in such a stage as that in 

 fig. 135, are identical w\th those presented in the later state, fig. 137. It appears to 

 me that the nuclei in the later state, merely occupy the same place as those in the 

 earlier. For here, in the muscle-cylinder, — or as Schwann has termed it, the 

 " secondary" cell, — the same process is in operation as, according to my observations, 

 is seen everywhere else in what have been called the primitive cells; namely, a con- 

 tinual change in the nucleus. A part continually passes off in the form of discs, 

 which are contained within the cylinder ; while a fresh supply of discs is continually 

 coming into view around an orifice, connecting apparently the interior and exterior of 

 the muscle-cylinder, or " secondary cell." This orifice, however, appears to be iden- 

 tical with that existing in the original cells, fig. 135. 



t On the Corpuscles of the Blood, Philosophical Transactions, 1840, Part II. p. 595. 

 I Compare /3 of fig. 135, with c of fig. 160, in my Third Series on Embryology, /. c. 

 MDCCCXLI. 2 I 



