THE BACK. 



Dissection. Dissection of the back is often almost wholly ignored ; ;md why 

 ignored? I would ask. Simply because (i) it is considered as belonging to a 

 region of the body called not practical ; because (2) its structures are somewhat 

 difficult to expose on dissection. Says one : " There are only two incisions in the 

 whole category of diseases of this region (i) for renal operations ; (2) for car- 

 buncles. Why, then, should one learn to dissect seven layers of muscles?" I 

 would answer, " If the former incision is made in the proper place, and the latter 

 deep enough, these alone are enough to justify careful study and dissection of this 

 area." I desire to accentuate the following : 



1 . The thick superficial fascia, and its very dense connective-tissue frame- 

 uork, since this is a favorite locality for boils and carbuncles, offering greater 

 resistance to pus than do all the other structures combined, between this and the 

 suboccipital triangle. (Law of projectiles.) 



2. The erector spinae and the quadratus lumborum, since these muscles 

 are guides to lumbar colotomy and lumbar nephrectomy and nephrotomy. 



3. The last rib, since in the above operations, nephrectomy and nephrotomy, 

 the pleura must not be cut or wounded, and the last rib is the guide. 



4. The complexus muscle, since this forms the roof of the suboccipital tri- 

 angle. On the floor of the triangle are the vertebral artery and suboccipital 

 nerve ; crossing the triangle, immediately under the complexus muscle, is the 

 great occipital nerve. 



5. The vertebral aponeurosis, since this separates the muscles which act 

 upon the shoulder girdle the first and second layers from the proper muscles 

 of the back viz., those that move the vertebral column by acting on the spinous 

 and transverse processes and the parts of the skull serially continuous therewith. 



6. The erector spinae, since this is the location of lumbago, the so-called 

 muscular rheumatism of the back. I wish you to note particularly in this con- 

 nection the anatomical reasons why the pain of lumbago need not be mistaken 

 for pain in diseases of the kidneys and surrounding viscera, of the rectum, and of 

 the uterus. The pain in lumbago (in any of the proper muscles of the back) is 

 logically located in the small of the back, because these muscles are supplied by 

 somatic nerves. It could not be mistaken for the above pains, because those 

 organs uterus, kidney, rectum have a sympathetic nerve-supply, and this pain 

 is reflected in the distribution of the anterior primary divisions of the somatic 

 nerves; the proper muscles of the back are supplied by the posterior pnmar_ v 

 divisions of the spinal nerves, and these latter have no sympathetic connections. 

 (See Fundamental Principles of Anatomy : Application of Law of Projectiles 

 in Cases of Pain Remote from Place of Injury.) 



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