54 SURGICAL APPLIED ANATOMY. [Chap, xxiv 



The amount of damage inflicted upon the cord will 

 vary, of course, with the magnitude of the accident ; 

 but, other things being equal, it will be found to be 

 more severely injured in fracture-dislocations of the 

 cervical and dorsal segments than in like lesions in the 

 lumbar spine. In the atlo-axial region the amount of 

 displacement that follows upon luxation of the t\ro 

 bones from one another is such that the cord is, as a 

 rule, severely crushed, and death ensues instantaneously, 

 as is seen in cases of death by hanging. In the cervical 

 and upper dorsal segments of the column the vertebral 

 bodies are small, the spine is mobile, the fractures 

 met with in the parts are usually due to indirect 

 -violence, and are associated with much displacement. 

 In the lower dorsal region, again, the greater rigidity 

 of the spine renders any displacement, when it does 

 occur, likely to be considerable. In the lumbar region, 

 on the other hand, it must be noted that the cord only 

 extends to the lower border of the first vertebra. The 

 bodies of the vertebrae, also, in this district, are very 

 large and cancellous, and can undergo a severe amount 

 of crushing without a corresponding degree of dis- 

 placement being produced. The part is also well 

 protected by the large intervertebral discs, and by the 

 immense masses of muscle that surround the spine in 

 the loins. Such portion also of the spinal medulla as 

 extends into the lumbar region is protected by tho 

 many cords of the cauda equina, which, by their loose- 

 ness and comparative toughness, tend to minimise the 

 effects of violence. 



The degree of displacement of bone required to 

 produce pressure effects upon the cord is often greater 

 than would be supposed. At post-mortem examina- 

 tions portions of injured vertebrae have been found 

 encroaching upon the spinal canal to a considerable 

 extent in cases where no evidences of damage to the 

 cord existed during life. Dr. J. W. Ogle reports the 



