TEE STUDY OF THE BONES. 



17 



Fig. 9. 



[the humero-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- 

 bation 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 

 ihas 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 

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

 I These bones are augmented in thickness by the formation of subperiostic 



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



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

 Itermed the marginal epiphyscs. 



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 

 i bones. When bones cease to grow, their nutri- 

 I 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- 

 I 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 

 H 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 

 I the appearance of minute nucleated cells, which 

 l 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 



jflat bones they are vertical to the margin. The 

 ij cells furthest from the seat of ossification are 

 [flattened and in close contact ; nearest that seat 

 1 they become enlarged and separated. 



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

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



CARTILAGE 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. 



