SECT 



104.] 



OSSEOUS SYSTEM. 



I97 



cartilage-capsules be regarded as secondary cell-membranes, aud their contents 

 as primordial cells ; and if the latter be admitted to grow out in a stellate 

 manner during the ossification, the harmony between the formation of the 

 lacuna? from the cartilage-capsules and plasm-cells is restored in all essential 

 points. If the opinion of Sharpey and II. Midler be correct, that in normal 

 ossification none or very few of the cartilage-corpuscles are directly me- 

 tamorphosed into bone-cells, and that the latter take their origin from the 

 cells of the first-formed medulla, then there would be no difference in the 

 formation of bone-cells from cartilage and from the periosteal layers, as, 

 indeed, Sharpey maintained long ago. 



With regard to the origin of the marrow-cells, Virchow is of opinion, that 

 they arise from the cartilage-cells enclosed in the ossifying cartilage-capsules, 

 which, by their multiplication, produce the small cells of the primitive marrow ; 

 whilst the latter is, in turn, transformed into fibres, vessels, nerves, fat- 

 cells, etc. According to what H. Midler has seen, there can be no doubt that 

 this view is correct. Hence it follows, that the bone-cells in bone formed 

 from cartilage, at all events, originate from cells which are the descendants 

 from the original cartilage-corpuscles. 



Fig. 86. 



§ 104. Changes in the Sub-periosteal Deposit. — The periosteum 

 of the bones which commence by cartilage is relatively very thick 

 and vascular, and, even in the fifth month of foetal life, consists of 

 ordinary connective tissue and fine 

 clastic fibres; the latter, as the 

 development advances, becoming 

 thicker and thicker, and occasionally 

 assuming the nature of thicker elastic 

 fibres. Upon the inner side of the 

 fully-developed periosteum, there is 

 an ossifying blastema firmly adherent 

 to the bone (fig. 86), so that when 

 the periosteum is pulled off, it gene- 

 rally remains lying upon it in the 

 form of a moderately thick, soft, 

 whitish-yellow lamella, which, when 

 examined microscopically, presents 

 a fibrous tissue with somewhat in- 

 distinct fibrils, like immature con- 

 nective tissue, and granular, oval, or 

 round nucleated cells, of o'Oi6'" to 001'" in size. If this lamella 

 be raised from the bone, it is found to be very intimately connected 

 with the most superficial layers of the latter j and upon its inner 

 side, detached osseous fragments and portions of reddish, soft 

 marrow, from the most superficial bone-spaces, are usually met 

 with. The denuded bone, when the lamella has been cautiously 



Transverse section, from the surface ot 

 the Qiaphysis of a metatarsal bone of the 

 calf; magnified 45 times. A. Periosteum. 

 B. Ossifying blastema. C. Young bone- 

 deposit, with wide spaces (a.), in which re- 

 mains of the ossifying blastema still exist, 

 and reticulated trabecule (6.), which are 

 rather sharplymarked off from the blastema. 

 D. Further developed bone with Haversian 

 canals (c), surrounded by their lamellae. 



