EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 181 



bone, but also around each of these canals. This explains the structure 

 of the cartilage of bone, the lamellae of which are concentric, partly 

 around the whole bone, and partly around the medullary canals. The 

 process by which the primary cells are formed is the following. The 

 cytoblastema, which is at first structureless or only finely granular, pre- 

 sents after a time round corpuscules. These corpuscules are in their 

 earliest recognizable condition, the nuclei of cells, around which cells 

 are subsequently to be developed. The nucleus is granular, and may 

 be either solid or hollow. The part of the nucleus first formed is the 

 nucleolus. Around this there is deposited a layer of fine granules. The 

 nucleus thus formed increases in size, and then the cell is developed 

 around it by the deposition of a layer of substance different from that 

 of the surrounding cytoblastema. This layer has at first no defined 

 outline ; but when it has become consolidated into a membrane, it ex- 

 pands by the continued addition of new molecules in the interstices of 

 the old ones. It thus becomes removed from the surface of the nucleus, 

 which remains attached to one point of the wall of the cell. This for- 

 mation of the cell around the nucleus is only a repetition on a larger 

 scale of the process by which the nucleus was formed around the nucle- 

 olus. The membranous wall of the cell differs in its chemical proper- 

 ties in different kinds of cells, and even in the same cell it varies in 

 chemical composition at different periods of its growth. Thus the 

 walls of vegetable cells, when first formed, are, according to Schleiden, 

 soluble in water, which is not the case with the cells which are perfectly 

 developed. The matter contained in the cell varies in a still greater 

 degree ; for example, it is in one case fat, in another pigment. In a 

 cell which is at first perfectly transparent, a granular deposit may gra- 

 dually appear, its formation commencing around the nucleus ; or, on 

 the other hand, a granular deposit contained in a cell may be gradually 

 dissolved. 



<jrtract3 anfc $toltractg from 



[From the Comptes Rendus, 1841.] 



Flourens researches on the Development of Bones. In this Memoir the 

 author treats on the general mechanism connected with the formation 

 of Bones, and deduces, from the experiments quoted in detail, these 

 three general conclusions ; 1. There is in bone, a formative apparatus, 

 which is the periosteum : 2. There is also an absorbing apparatus, viz. 



