o40 SPECIAL HISTOLOGY. 



possesses nerves of only one kind. It is not, however, by this, intended 

 to imply that the nerves of bones do not convey conscious perceptions ; 

 it is possible that, through them, we obtain a certain degree of know- 

 ledge of the processes going on in the bones, of the degree of fulness 

 of the vascular system, the mechanical influences to Avhich they are 

 exposed from without in the movements caused by the action of the 

 muscles, the weight of the body, or of external objects, in lifting 

 weights, mastication, &c. ; but in any case this knowledge would be 

 very indeterminate, and the sensation excited not definitely localized, 

 being confused in the general feelings of fatigue, efibrt, or relaxation. 

 On the other hand, it is quite certain that the bones, in man, in many 

 diseases, and in consequence of mechanical injury, afford pain, which 

 latter fact has also been frequently noticed in animals, at all events, 

 upon irritation of the larger nervous trunks of the diaphyses. In man 

 the apophyses, in particular, and the vertebral and cranial bones, seem 

 readily to become painful, which is explained by the considerable number 

 of nerves immediately in the spongy substance. The compact substance, 

 on the other hand, might probably be regarded as scarcely obnoxious to 

 pain ; as, for instance, in resections, but not so perhaps the periosteum, 

 which less from its own nerves than as the vehicle of those of the bones 

 before they enter their destination, must naturally be affected in the 

 same way that they are. Whether the nerves of the bones through 

 which, perhaps, the conscious perceptions, but in any case the painful 

 impressions are conveyed, be identical with those through which the' 

 reflex actions, above referred to, are carried on, is not determined ; but, 

 looking at the origin of most of the bone-nerves from the cerebro-spinal 

 nerves, such an opinion might perhaps be maintained, it being premised 

 that the connections of the nerves with the brain are to be regarded as 

 less intimate than in the case, for instance, of the cutaneous nerves. I 

 would, in addition, call attention to the remarkable occurrence of nerves 

 in the cartilage of the septutn narium in the Calf, although I am unable 

 to say anything more with respect to their nature than with regard to 

 that of the nerves of bone. 



On the subject of the numerous pathological changes which occur in 

 the bones, only some brief remarks can here be made. Fractures readily 

 unite, under but moderately favorable circumstances, by true bone-sub- 

 stance, which, in the cylindrical bones of animals is preceded by the 

 formation of a true cartilage, a fact of which I and others are satisfied ; 

 whilst, according to Paget, this rarely appears to be the case in man. 

 In the spongy bones, in fractures within the articular capsules, and 

 "under unfavorable circumstances, the fractured ends frequently unite 

 merely by a fibrous callus, a sort of articulation being formed between 

 them. After loss of substance the osseous tissue is readily regene- 

 rated ; and it is the periosteum especially, which, in this case, as in 



