PROGRESS OF MICROSCOPICAL SCIENCE. 17 



1. Formation of the First Vessels in Bone, developed from Cartilage ; 

 Origin of the Osteoblasts and Osteoclasts. — In this paragraph Kolliker 

 confirms the assertion of Loveu, Sharpey, and especially of Gegenbaur, 

 that the marrow, in all its constituent elements, of bones, which are 

 preformed as cartilage, originates from the perichondrium or the 

 periost respectively. The circumstances that led Kolliker to this 

 conclusion are these : — (a) In the cartilage of the epiphyses and in 

 the short bones the well-known processes of the perichondrium, which 

 project into the cartilage, and which contain, besides blood-vessels, a 

 fibrillar matrix, with spherical and spindle-shaped cells, do not deve- 

 lop from the cartilage (Virchow), but from the perichondrium. The 

 cartilage itself does not become dissolved, as supposed, by the pro- 

 gressive growth of those processes, but is simply pushed aside. (/>) In 

 the diaphyses of the phalanges of the embryo of calf, sheep, pig, and 

 man, it can be shown that after the appearance of the first thin peri- 

 ostal crust of true bone-substance and the first calcification of the 

 inner cartilage, processes grow from the osteogenetic layer of the 

 periost, which spread out gradually towards all sides, and jjr netrate 

 into the cavities of the cartilage-capsules. The tissue of which these 

 j)rocesses consist is similar to that of the perichondral processes, 

 previously mentioned, excejjt that it is more loose, and that it con- 

 tains more spherical elements. From these latter the osteoblasts and 

 osteoclasts (myeloplaxes) take their origin. By the growth of these 

 processes the calcified parts of the cartilage-matrix are gradually 

 absorbed, in which proceedings the osteoclasts play an important part. 

 The cartilage-cells themselves do not transform into cells of the 

 marrow, (c) Exactly the same takes place at the ossification-margin 

 of the diaphysis, for here the elongated vascular processes, which 

 gradually penetrate from the diaphysal extremity into the cartila- 

 ginous epij)hysis, are also ofisprings of the periostal processes. Those 

 vascular processes are always and everywhere sharply defined from 

 the cartilage. Osteoclasts are generally not to be met with at the 

 terminal points of the vascular processes, but they occur in great 

 numbers near the ossification-margin ; so that they play certainly a 

 part in the resorption of calcified cartilage-matrix, but not in the 

 dehiscence of the cartilage-cavities. 



2. Growth of Bones in Length. — By the well-known method of 

 feeding very young animals with madder, Kolliker arrived in agree- 

 ment with Oilier and Humphry to the following conclusions as regards 

 the growth of bones in length : — (a) In long tubular bones with ej^i- 

 physes on both extremities, that extremity of the diaphysis grows 

 quicker whose epij)hysis remains longer separated, (b) Short tubular 

 bones, with only one ej^iphysis, grow quickest at the diaphysis touching 

 that epiphysis (calcaneous, metatarsi, metacarpi, phalanges), (o) All 

 free edges and apophyses of any bone show a very marked growth 

 (crista ossis illi, tuber ischii, processus spinosi et transversi, processus 

 xyphoideus sterni, processus styloideus ulnae), (d) The same holds 

 good with certain extremities of long bones, which are provided with 

 a considerable layer of cartilage — e. g. the ribs. (e) Short bones, 

 with and without epiphyses, grow pretty equally on all cartilaginous 



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