THE STUDY OF THE BONES. 17 



the Lumero-radial articulation grows fastest ; while in the abdominal limb 

 the extremity most distant from the femoro-tibial articulation grows the least! 

 Concerning the growth of the bones in thickness, this occurs by the ossifi- 

 cation of the deep layer of the periosteum called the osteogenetic layer. The 

 experiments of the above-named authors have irrefutably demonstrated this 

 fact. The formation of bony tissue in the deep layer of the periosteum is very 

 active during the youth of animals ; but it soon slackens, and in advanced 

 age ceases completely. In the first period of life, in proportion as the new 

 layers are added to the surface of the bone, the old layers, those nearest the 

 medullary canal, disappear by resorption. Later, the process of resorption 

 exceeds that of formation, which is, in old age, completely annihilated. It 

 has also been observed that the formation of a certain quantity of the 

 osseous elements takes place on the inner face of the medullary canal, at the 

 expense of the medullary tissue. In the flat bones, the primitive centre of 

 ossification is developed nearly in the middle, and the calcareous salts are 

 afterwards deposited in radiating lines from this spot towards the periphery. 

 These bones are augmented in thickness by the formation of subperiostio 

 layers, and by the development of the spongy tissue between their two 

 compact laminse ; they increase in width by the ossification of what are 

 termed the marginal ejnphyses. 



The short bones grow from the periosteum 

 and the epiphysery cartilages, when they possess 

 complementary centres. 



Nutrition.- — The experiments which consisted 

 in feeding young animals with madder, and 

 afterwards examining their osseous system, have 

 for a long period demonstrated the nutrition of 

 bones. When bones cease to grow, their nutri- 

 tion becomes less active ; but it is evident that 

 it does go on, in order to maintain the organic 

 matter of the osseous tissue in a proper con- 

 dition. 



(Professor Owen has explicitly and concisely 

 stated the development of bone to occur as fol- 

 lows : — " The primitive basis, or ' blastema ' of 

 bone is a transparent glairy matter containing 

 numerous minute corpuscles. It progressively 

 acquires increased firmness ; sometimes assuming 

 a membranous or ligamentous state, usually a 

 gristly consistence, before its conversion into 

 bone. The change into cartilage is noted by 

 the appearance of minute nucleated cells, which 

 increase in number and size, and are aggregated 

 in rows, with intercellular tracts, where the 

 ossification is about to begin, as in fig. 9. 



These rows, in the cartilaginous basis of 

 long bones, are vertical to its ends ; in that of 

 flat bones they are vertical to the margin. The 

 eeUs furthest from the seat of ossification are 

 flattened and in close contact ; nearest that seat 

 they become enlarged and separated. 



The first appearance of bone is that of minute granules in the inter - 

 columnar and intercellular tissue. Canals are next formed in the bone by 



CAKTILAGB AT THE SEAT OP 

 OSSIFICATION, showing at its 

 lower portions the clusters 

 of cells arranged in columns, 

 each of which is inclosed in a 

 sheath of calcified intercellular 

 substance. 



