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



have been on cartilage in this more advanced state, that observations heretofore have 

 been principally made. And the figures given by Schwann of cartilage-f-, show, I 

 think, the continued existence of centres of this kind. 



143. A suggestion offered in one of ray former memoirs :};, seems to have been 

 realized by the observations recorded in this paper ; for the elements of cartilage are 

 certainly the seat of changes essentially the same as those we formerly witnessed in 

 the cells succeeding the germinal vesicle in the ovum. 



144. We also find that cartilage exhibits centres, such as those we have seen to 

 exist in the epithelium (par. 119.), — in the black pigment of the eye (par. 120.), — in 

 cellular tissue (par. 135.), — as are to be recognized, I think, in the "Ganglion-glo- 

 bules," — and the most remarkable of which centres is the ovum. But in these special 

 centres there is to be witnessed no other than the same process, as that which operates 

 in the nucleus of every cell. 



145. Fig. 116 J. represents the outline of very large cells, filled with other cells. 

 The large cells had the appearance of altered blood-corpuscles ; the colour being also 

 pale red. The nuclei were for the most part blood-red, and not distinguishable from 

 young corpuscles of the blood (fig. 106.), lying near them. From the great length 

 of the object formed by the large cells just mentioned, and from its general appear- 

 ance, I am disposed to regard it as the foundation of the cartilage destined to form 

 a bone ; but the object, though consisting of large cells, was so minute, that an 

 opinion here must be cautiously expressed. 



146. The extremity of the 'incipient beak, as well as that of a claw, from a foetal 

 duck, on the 13th day of incubation, were found to be in a state of the same kind 

 as the forming cartilage in fig. 119; and there was observed a transition out of cor- 

 puscles having the same appearance as corpuscles of the blood. 



147. A like origin has seemed to be presented by the elements of feathers in the 

 chick : but my observations here have been but few. 



148. Though rather out of place, it may be mentioned, that in the Tadpole which 

 yielded the drawing fig. 121, 1 saw what appeared to be the foundation of a ligament, 

 also having an origin in corpuscles which presented the same appearance as corpus- 

 cles of the blood, and seemed to be arranging themselves into a fibre. 



The Elements of Nervous Tissue compared with Corpuscles of the Blood. 



149. The optic nerve in the Tadpole of 4^'" to 5'", seen as it is entering the eye- 

 ball, is very easily found, and there is not much danger of any other object being 

 mistaken for it. My observations on the optic nerve, at this early period, have been 

 very numerous, and, it may be added, highly satisfactory. 



t L. c. Tab. L figs. 5-9. Tab. IIL figs. 1, 2. : Researches in Embryology : Third Series, /. c, par. 393. 



