500 SURGICAL APPLIED ANATOMY. [Chap. xxiv. 



and there is little doubt that the long-felt pain and 

 inconvenience often depend upon some synovitis of 

 the vertebral joints. In a few cases this synovitis 

 has gone on to suppuration, and in one instance at 

 least the pus so formed found its way into the 

 spinal canal, and induced some mischief in the cord. 



Fractures and dislocations of the spine. 

 The effects of violence applied to the column are much 

 diminished by the general elasticity of the spine, by its 

 curves, and by the circumstance that it is composed 

 of a number of separate segments. Each vertebra 

 meets the one immediately above or below it at three 

 points of contact, the body and the two articulating 

 processes. The bodies are separated by the inter- 

 vertebral disc, which acts as an excellent spring or 

 buffer in modifying the effects of violence. The ar- 

 ticulating processes are more or less wedge-shaped, the 

 thin edge of one being applied to the base of the other. 

 When a force is applied to the column that tends to 

 compress the vertebrae together, the bases of the two 

 wedges are brought in more and more close relation, 

 and thus an increasing resistance is offered to the com- 

 pressing power. 



The parts of the spine most liable to injury are 

 (1) the atlo-axial ; (2) the cervico-dorsal ; and (3) the 

 dorso-lumbar. In the atlo-axial region the parts not 

 only enjoy a very considerable degree of movement, 

 but are very directly influenced by many forms of 

 violence applied to the head. In the two other regions 

 it will be noted that a flexible part of the spine joins a 

 comparatively rigid segment of it, and thus violence 

 applied to the column in either of these districts is 

 apt to be concentrated rather than diffused. The 

 mechanism is in a way illustrated by the circumstance 

 that a fishing-rod when it snaps commonly breaks near 

 a joint, that is to say, at a spot where a flexible seg- 

 ment of the rod meets a less elastic portion. In the 



