478 



APPLIED ANATOMY. 



rior edge of the scapula is another small triangle. Its upper side is formed by the 

 trapezius, its lower by the latissimus dorsi, and its outer by the posterior edge of the 

 scapula. As the lung is nearest the surface at this point it is often chosen for physical 

 examination, puncture, etc. 



THE VERTEBRAL COLUMN. 



Normally the spinal column is composed of seven cervical, twelve dorsal, five 

 lumbar, five sacral, and four to five coccygeal vertebrae. The sacral vertebrae tend 

 to fuse together, forming a single bone, the sacrum. This fusion is complete at the 

 twenty-fihh year. The coccygeal vertebrae join later, fusion occurring in middle life. 



Sometimes in advanced age the coccyx and sacrum 

 fuse together. The cervical vertebrae are almost 

 always seven in number, but both the dorsal and 

 lumbar vary much more frequently than is usually 

 supposed. The occurrence of thirteen instead of 

 twelve ribs on a side is not uncommon and I have 

 seen skeletons with only eleven. A rudimentary- 

 cervical rib also occasionally occurs. 



The tips of the spinous processes of the cervical 

 vertebrae, the first two dorsal, and last four lumbar, 

 pass almost horizontally backward and are there- 

 fore nearly opposite the bodies of the vertebrae to 

 which they are attached. The tips of the spines 

 from the third to the last dorsal inclusive, however, 

 are opposite the bodies of the next vertebrae below 

 them, being inclined downward, while the tip of the 

 first lumbar is about opposite the intervertebral disk 

 beneath. 



Curves. At the third month of intra-uterine 

 life there is only one large curve, convex poste- 

 riorly. At birth there are two curves, each convex 

 posteriorly, a dorsal and sacral, probably to accom- 

 modate the thoracic and pelvic viscera; after the 

 erect position is assumed the cervical and lumbar 

 curves become established. The cervical passes 

 into the dorsal curve at the middle of the second 

 thoracic vertebra and the dorsal into the lumbar at 

 the middle of the last thoracic vertebra. (Fig. 

 478). Laterally, there is a slight curve in the 

 dorsal region with its convexity to the right, prob- 

 ably due to the increased use of the right hand. 



Movements. Flexion and extension are free 

 in the neck and lumbar region, rotation is slight in 

 the cervical region, free in the upper portion of the 

 dorsal, and gradually diminishes to be absent in the 

 lumbar region. 



I. lumbar 



I. sacral 



\ -I. coccygeal 



DEFORMITIES OF THE SPINAL COLUMN. 



The weight of the head is borne on the condyles 

 FIG. 478. Lateral view of the adult spine, of the occiput, and a perpendicular let fall from the 

 .ts curves. (Piersoi.) condyles passes through the points where the spinal 



curves pass one into the other and thence through the anterior edge of the promontory 

 of the sacrum. Hence if one curve is altered by injury or disease it is of necessity 

 accompanied by a corresponding change in the curve on the opposite side of the 

 perpendicular line. The first is called the primary curve and the other the second- 

 ary one. In anteroposterior curvatures these curves are exaggerations of the normal 

 curves but in lateral curvatures they are newly formed because there is, practically, 



