FORMATION OF THE TISSUES BONE. 487 



ages, accounting for the variations in the rapidity of its nutrition and repara- 

 tion, is well displayed by the effects of Madder. When animals are fed 

 with this substance, it is found that their bones become tinged with it, on 

 account of the affinity of the colouring principle for phosphate of lime. In a 

 very young animal, a single day suffices to colour the entire skeleton ; for in 

 these there is no osseous material far from the vascular surface : when sec- 

 tions are made, however, of the bones thus tinged, it is found that the colour 

 is confined to the immediate neighbourhood of the Haversian canals, each of 

 which is encircled by a crimson ring. In full-grown animals, the bones are 

 very slowly tinged, because the osseous texture is much more, consolidated 

 and less permeable to fluids than in earlier life; and because, owing to the 

 formation of new lamellae, the outer ones are pushed to a greater distance from 

 the Haversian canals. 



632. The Regeneration of Bone, after loss of its substance by disease or 

 injury, takes place more completely perhaps than that of any other tissue, 

 except the Areolar ( 638). This is partly due to its high degree of vascu- 

 larity, and partly to the simplicity of its structure. When we consider the 

 great importance of the mechanical support afforded by Bone, in every func- 

 tion of the -body, and the necessity for an entire reparation before that support 

 can be obtained, we perceive that no half-measures (such as are adopted in 

 the repair of muscles, ligaments, &c.,) would here suffice. The ordinary 

 nutrition of Bone takes place through thie vessels of the Periosteum and those 

 of the Medullary membrane, from both of which sets the branches are given 

 off that traverse the Haversian canals : the outer layers, however, are chiefly 

 supplied from the Periosteum, and the inner from the Medullary membrane ; 

 so that, when the external membrane is destroyed, the outer layers die, whilst 

 the inner layers suffer no interruption of their supply of nutriment received 

 through the lining membrane. In the disease termed Necrosis, it is seldom 

 (if ever) that the whole thickness of the bone loses its vitality; either the 

 outer or the inner layers suffer; and whichever part remains alive, it becomes 

 increased in thickness by Inflammation, and by the succeeding processes. 

 Plastic lymph is thrown out in layers ; this becomes organized, converted into 

 Cartilage, and finally into Bone. When a bone is fractured, the same kind 

 of process takes place. Organizable lymph is effused, not only from the ves- 

 sels of the bone and its membranes, but from those of the surrounding struc- 

 tures ; this gradually becomes vascular, and in time assumes a cartilaginiform 

 appearance, although its structure is probably not exactly the same with that 

 of ordinary cartilage. Ossification usually commences at the extremities of 

 the fractured bone ; and, if these be near each other, they are soon united by 

 Callus. If they be distant, however, their union is a very gradual process. 

 It is not true fas maintained by some) that ossification takes place only in the 

 parts where the new substance is connected with old bone. Mr. Gulliver* 

 has remarked that, when the broken portions of bone form an angle, there is 

 quite a distinct centre of ossification, commencing in the soft parts that lie 

 between the sides of the angle. This new bone, being a provision to meet 

 the exigences of an irregular case, is termed by Mr. G. the accidental callus; 

 it forms a support between the fragments, in a situation which is exactly that 

 of the greatest mechanical advantage. Though for some time quite uncon- 

 nected with the old bone, it soon becomes united to the regular callus. A 

 deposit of osseous matter also takes place occasionally on the interior of the 

 Periosteum, when this has been separated from the bone by necrosis of the 

 latter, and by the collection of fluid between them ; whether this be true Bone, 

 however, has not been ascertained. It is quite certain that in this, as in other 



* Gerber's Anatomy, p. 13, note,- and Edinb. Med. & Surg. Journal, vol. xlvi., p. 313. 



