1142 SURGICAL AXD TOPOGRAPHICAL AX ATOMY 



(5) extra-peritoneal fatty tissue; (6) peritoneum. If the hernia come through 

 above the umbilicus, or just to one side, the coverings will be much the same; but, 

 instead of the layer from the umbilical scar, there ^vi]l be one from the linea alba. 



THE BACK 



Median furrow. — This is more or less marked according to the muscular devel- 

 opment, lying between the trapezii and complexi, in the cervical region, and the 

 erectores spinae lower down. The lower end of the furrow corresponds to the 

 interval between the spines of the last lumbar and the first sacral vertebrae 

 (Holden). 



Vertebral spines. — Those of the upper cervical region are scarcely to be made 

 out even by deep pressure. That of the axis may be detected in a thin subject. 

 Over the spines of the middle three cervical vertebrae is normally a hollow, owing 

 to these spines receding from the surface to allow of free extension of the neck. 

 The seventh cervical is prominent, as its name denotes. Between the skull and 

 atlas, or between the atlas and axis, a sharp-pointed instrument might penetrate, 

 especially in flexion of the neck. 



Of the thoracic spines, the first is the most prominent; the third should be 

 noted as on a level with the inner end of the scapular spine, and in some cases with 

 the bifurcation of the trachea; that of the seventh with the lower angle of the 

 scapula; that of the twelfth with the lowest part of the trapezius and the head of 

 the twelfth rib. The obliquity and overlapping of the thoracic spines is to be 

 remembered. 



Of the lumbar spines, the most important are the second, which corresponds to 

 the termination of the cord, and that of the fourth, which marks the highest ])art 

 of the iliac crests and the liifurcation of the abdominal aorta. The lumliar spines 

 project horizontally, and correspond with the vertebral bodies. Tlie third is a 

 little above the umbilicus. 



Owing to the obliquity of the thoracic spines, most of them do not tally with 

 the heads of the corresponding ribs. Thus, the spine of the second corresponds 

 Avith the head of the third rib; the spine of the third with the head of the fourth 

 rib; and so on fill Ave come to the eleventh and twelfth vertebrae, Avhich do tally 

 with their corresponding ribs (Holden). 



• The lower ribs may be felt outside the erector spinae, but, in counting them from 

 below, it must be remembered, as pointed out by Holl, that in quite a considerable 

 percentage the last rib is so abnormally short that it does not reach as far as the 

 outer border of the sacro-lumbalis; or so rudimentary as to more resemble a 

 transverse process. In these cases the lower end of the pleura may pass from the 

 lower part of the tAvelfth thoracic vertebra, almost horizontally to the loAver edge of 

 the eleventh rib. 



Muscles. — The student will remember the great number and complexity and 

 the numerous tendons of the muscles Avhich run up on cither side of the spine; 

 the firmness and inextensibility of their sheaths; the large amount of cellular 

 tissue betAveen them; and the fact that towards the nape of the neck these 

 muscles lie exposed instead of being protected in gutters, as is the case beloAv: all 

 these anatomical points explain the extreme painfulnoss and ol)stinacy of sprains 

 here. 



Trapezius. — To map out this muscle, the arm should be raised to a right angle 

 Avith the spine. The external occipital protuberance should be dotted in, and the 

 superior nuchal line passing out from this; beloAv, the tAvelfth thoracic spine should 

 be marked; and externally, the outer third of the clavicle and the commencement 

 of the sca])ular spine. Then a line should be draAvn from the protuberance A-erti- 

 cally dowuAA'ards to the twelfth thoracic spine; a second from al)0Ut tlie middle of 



