CAEIES OF THE SPINE 127 



arterial twigs are so numerous. For the same reason, the 

 adjacent joint is comparatively rarely involved. The separated 

 diaphysial periosteum may, if the patient lives, throw down fresh 

 bone at some distance from the necrosed shaft, and it will be this 

 newly-formed bone which will support the limb after the removal 

 of the sequestrum. Therefore it follows that if that portion of 

 the extremity is attacked which only contains a single bone, it is 

 absolutely necessary that a large quantity of ensheathing bone 

 should be thrown out before the necrosed portion is removed, 

 otherwise great and permanent shortening of the limb will 

 occur. 



Chronic Abscess of Bone. Whether due to tuberculous or 

 staphylococcic infection, it is the cancellous tissue at the epiphy- 

 sial end of a long bone which is usually the seat of a chronic 

 abscess. Enlargement occurs, and a tender spot is often present 

 evidencing the line along which the pus is endeavouring to obtain 

 an exit, and indicating the spot at which the abscess should be 

 attacked. It is interesting to note that the pus finds its way out 

 through the bone to the skin much more frequently than through 

 the articular cartilage into the joint, the non- vascular cartilage 

 being a highly resistant structure. 



Caries of the Spine. The deposit of tubercle bacilli apparently 

 takes place most usually in the newly formed bone deep to the 

 epiphyseal discs of the centrum. The regions commonly affected 

 are those where most movement occurs, hence the dorsi-lumbar 

 and cervico-dorsal junctures are frequent sites of the disease. 



As destruction of the bone forming the body progresses, the 

 weight of the superincumbent parts causes the centra to be 

 pressed together, whereby the spinous processes become prominent 

 in an angle, and give rise to the typical kyphosis or angular 

 curvature. 



The spinal nerve roots issuing from the intervertebral fora- 

 mina are liable to be irritated by the inflammation associated 

 with the tuberculous granulation tissue, hence pain, referred to 

 the peripheral distribution of these nerves, is a very common 

 occurrence. Consequently a child suffering from lower dorsal 



