BACK. 



307 



without some more complicated provision : 

 thus the inferior intercostal veins could not join 

 the inferior cava, where the latter is imbedded 

 in the liver, without perforating the diaphragm ; 

 neither could the middle and superior inter- 

 costal, the mediastinal, and the bronchial 

 veins arrive at the superior cava or at the right 

 auricle of the heart without a much more 

 complex disposition of all these parts than 

 we observe. 



For the BIBLIOGRAPHY see that of VENOUS 

 SYSTEM. 



(Robert Harrison.) 



BACK, REGION OF THE (surgical 

 anatomy). Under this denomination, which is 

 of Saxon origin, it is intended to describe the 

 posterior regions of the body situated between 

 the head and the pelvis, including a cervical, 

 a dorsal, and a lumbar region, varying in breadth 

 in these different portions, and corresponding 

 in length to that of the spine. The skeleton 

 of this extensive region consists of the spinal 

 column, and a portion of the ribs, and to the 

 former of these it is chiefly indebted for its 

 longitudinal curvatures. Thus we find it con- 

 cave in the cervical and lumbar portions, 

 convex in the dorsal. (See SPINE.) 



In its whole course from the os occipitis to 

 the base of the sacrum, we observe a central 

 depression occasioned by the prominence of 

 muscular masses on each side. In weak and 

 emaciated subjects a rugged ridge takes the 

 place of this depression ; the ridge is the series 

 of spinous processes which have little or no 

 muscular covering, and are hid when the mus- 

 cles on each side are much developed. At the 

 junction of the cervical and dorsal portion, 

 however, the ridge is scarcely ever obscured, 

 because there the spines are very long and the 

 muscles thin ; and again, the depression at the 

 top of the neck is only rendered deeper by 

 emaciation. 



The length of the cervical region is well de- 

 fined by the external tuberosity of the os occi- 

 pitis above, and by the prominent spine of the 

 last cervical vertebra below. Its breadth, at the 

 upper part, extends from one mastoid process 

 to the other; in the middle it becomes nar- 

 rower, and inferiorly it again spreads out 

 almost to the acromio-clavicular articulations. 

 Its length and breadth vary in different indi- 

 viduals. In general it is broader, propor- 

 tionally, in the male than in the female, espe- 

 cially at the upper part, where, according to 

 Gall, it may be considered a measure of ama- 

 tiveness. At the top of this region we see a 

 remarkable depression, called the suboccipital 

 fossa, or cervical fossa ; its existence depends 

 on the absence of a spinous process in the 

 atlas, while the muscles on either side, chiefly 

 the complexi, stand out boldly. In fat persons 

 a quantity of adipose substance fills up this 

 hollow and nearly obliterates it. The upper 

 third of the neck, and in some persons much 

 more, is covered with hair. This part is tech- 

 nically called nucha, a term of Arabian origin. 

 Its common appellation is nape of the neck. 

 (See Jig. 2J 



The dorsal region corresponds in length to the 

 twelve dorsal vertebra, with their intervertebral 

 substances, and in this dimension it is well de- 

 fined, but its breadth is not so settled ; anato- 

 mists bound it by the angles of the ribs on 

 either side, while surgical writers extend it 

 somewhat farther. This region is convex from 

 above downwards, and from side to side also, 

 if we overlook the slight central depression. 



The lumbar region extends from the last 

 dorsal vertebra to the base of the sacrum, arid 

 on each side to the outer margin of the sacro- 

 lumbalis muscle. These bounderies can gene- 

 rally be seen and felt without difficulty. It is a 

 little concave from above downwards, convex, or 

 nearly plane, from side to side, with the central 

 depression slightly marked. 



Integuments. The integuments of the back 

 are every where strong and coarse. They are 

 particularly so over the spinous processes, 

 where an imperfectly marked raphe exists; 

 they are also more fixed along that line than 

 elsewhere, on account of the density of the 

 cellular tissue which connects them to the su- 

 pra-spinal ligament, and in many subjects the 

 raphfe is hairy. 



The sensibility of the skin is much less on the 

 posterior than on the anterior surface of the body ; 

 the nerves and vessels are not so numerous, nor 

 is its organization so high. Hence its resistance 

 to the action of vesicatories and rubefacients, 

 which must be stronger, or applied for a 

 longer period to produce the required effect. 

 The skin is also very unyielding, so that col- 

 lections of matter do not readily make their 

 way to the surface, and if not opened early may 

 spread under it extensively. 



Subcutaneous cellular tissue. On raising the 

 integuments a layer of cellular substance is 

 observed, not containing much fat. It is strong, 

 coarse, and filamentous, and adheres to the 

 skin more than to the muscles. In passing a 

 seton in the neck we pinch it up with the skin, 

 and transfix it without touching the muscles, 

 which could not be wounded with impunity. 

 Along the middle line this fascia is more con- 

 nected to the deeper parts than it is on either 

 side, and especially in the dorsal region. 



This cellular tissue is frequently the seat of 

 post-mortem congestions and effusions arising 

 from the gravitation of the fluids to so depen- 

 dent a position; hence we generally find it 

 either very vascular or infiltrated with fluid, 

 in a state quite resembling anasarca. 



A very fine layer of cellular tissue, under- 

 neath this again, closely adheres to the mus- 

 cular fibre, and a good deal of motion may take 

 place between these two layers. 



The arteries which supply the skin and fascia 

 in the neck are branches of the occipital, the 

 cervicalis profunda, and the transversalis colli, 

 to which the vertebral and transversalis humeri 

 may contribute a little. In the dorsal region 

 the posterior scapular and the dorsal branches 

 of the intercostals principally supply these 

 parts ; and in the lumbar region we have the 

 posterior branches of the lumbar arteries. 

 None of these approach the skin in their undi- 

 vided state, so that superficial wounds here can 



