484 



LECTURE XIX. 



FIG. 135. 



and often penetrates, in the form of spicula, nodules, 

 and protuberances, to a very considerable depth into 

 the neighbouring soft parts. It is self-evident that in 

 these cases we have by no means to deal with any proli- 

 feration of the periosteum in any outward direction, but 

 that an ossifiable tissue arises out of the interstitial con- 

 nective tissue of the neighbouring parts. Of this it is 

 very easy to convince oneself, because osseous spicula 

 are found shooting up in the interstitial tissue of the 

 neighbouring muscles. In the preparation from the 

 fractured ribs places are still to be found in the external 

 parts, where fat has been included 

 in the ossification. It cannot be said 

 therefore that the formation of callus 

 around fractured parts is altogether 

 a periosteal formation ; in all cases 

 where it takes place with a certain 

 abundance, it transgresses the limits 

 of the periosteum, and invades the 

 connective tissue of the surrounding 

 soft parts. 



There is a second kind of callus- 

 formation completely different to 

 this that namely, which takes 

 place in the midst of the bone from 

 the medullary tissue. 

 At the moment when the bone in a case of fracture 



Fig. 135. Transverse fracture of the humerus with formation of callus, about 

 fourteen days old. On the outside is seen the porous capsule of the callus pro- 

 duced from the periosteum and soft parts, the innermost layer on the right side 

 being still cartilaginous. On the left lies detached a fragment shivered off from 

 the cortex of the bone. The two fractured ends are connected by a (dark-red) 

 fibrinous layer of haemorrhagic origin ; the medulla on both sides is very dark 

 (owing to hyperaemia and extravasation), in the lower fragment several porous 

 islands of callus are seen which have been produced by the ossification of the 

 medulla. 



