GROWTH OF BONE. 43 



point, and the ossificrays pass off in a straight direction, as seen 

 in Fig. 6, page 41. 



Many of these bones, as well as of those in other parts of 

 the body, are of such irregular shape, as to be inca]>able of 

 being formed of fibres radiating from a single centre ; they are, 

 therefore, developed from several centres, the rays of which 

 finally meet and inosculate. The development of the thick 

 bones, and the epiphysis of the long bones, take place in accord- 

 ance with the same laws. 



Growth of Bones. In all the long bones, the extremities or 

 epiphyses, are developed in separate pieces and between them 

 and the ossified shaft there is a cartilaginous lamen, which does 

 not disappear till the bone has attained its full development. 

 The bones increase in length by the continuous deposit of new 

 ossific matter in this lamen of cartilage, which seems retained 

 there as a soft bed for that purpose. As soon as the bone has 

 attained its full length at puberty, the lamen disappears, and 

 the epiphysis and shaft are consolidated, as seen in Fig. 3, where 

 2 is the layer of the cartilage, beginning to disappear at one 

 point. The long bones increase in diameter, by the successive 

 addition of new bony matter between the periosteum and bone. 

 It is said to be deposited from the periosteum itself: but that 

 opinion is incorrect, for no membrane can form a tissue, so 

 much at variance with its own structure. It is the blood- 

 vessels which merely ramify minutely through the periosteum, 

 that deposit the matter upon the surface of the bone, precisely 

 as they do in the centre. This mode of growth in diameter by 

 concentric circles, has been proved by experiments made with 

 mixing madder at intervals in the food of animals, by Duha- 

 mil,* Hunter, Professors Homer, Mussey, myself, and others. 

 On killing the animals, red rings were found surrounding the 

 bones, alternated with white ones corresponding to the periods of 



* Duharail who was no anatomist, considered the growth of bones, as analo- 

 gous to the vegetation of plants. He placed a silver ring upon the bone of a 

 young animal, which he afterwards fed interruptedly on madder. The white 

 and red strata alternately covering the ring as he found on killing the animal, 

 he erroneously considered not deposited on the outer surface, but formed by the 

 expansion of the bone bulging over it as takes place in plants. r. 



