KATURE OF THE INTERVERTEBRAL SUElSTANCE. 



213 



composed of materials which render it very pliant, though 

 not at all elastic, fitting it to keep the vertebrae at the pro- 

 per distance from each other, so as to admit of the actioft«of 

 the lateral elastic ligaments. 



When this knowledge is applied to the treatment of cur- Curvature of 

 vatures of the spine, a complaint so commonly met with in the spins. 

 young women., wiiose strength does not bear the necessary 

 proportion to the growth of the body, it will show the great 

 impropriety of overstretching the intervertebral ligaments, 

 since in that state the central substance no longer supports 

 the vertebrae, and the joints must lose their proper firmness, 

 which will be attended with mainy disadvantages. 



As the principal motive, which induces me to prosecute the Advania^as of 

 laboriouis researches of comparative anatomy, is to attain si anl^Jomv"^^ 

 more complete knowledge of the structure and functions of 

 the human body, than can be acquired \n any other way ; 

 and to apply this knowledge to the most useful of all pur- 

 poses, the cure of dieases ; the success which has attended 

 my labours, in the present instance, affords me particular sa- 

 tisfaction ; it encourages me in the pursuit of those inqui- 

 ries, and holds out an invitation to others, by showing them 

 that the paths of nature, however frequently they have been 

 traced, are not yet sufficiently explored. 



Explanation of the Plate, 



A longitudinal section of one of the intervertebral joints Explanation 

 of the squalus maximus, after the fluid had been evacuated, ^^^^^ p\At&. 

 and the parts had been steeped in water. 



PI. Y,a aa a. The section of the vertebra, to show its shape 

 and the two concave surfaces which form the intervertebral 

 cavities. The vertebra itself is partly bone, and partly 

 transparent cartilage ; the bony portion forms the two cup- 

 like cavities, and the intermediate substance consists of bony 

 cells in form of lozenges filled with cartilage. 



The cavity of the joint is in its contracted state, and the 

 inner portion of the lateral ligaments, which is made up of 

 thin layers of a loose texture, has its interstices loaded with 

 water, which makes it project into the cavity of the joint 

 more than it could do in a natural state. 



The 



