TOPOGRAPHY OF THE ORGANS 



THE SKELETON 



The vertebral column is about 4 cm. wide in the upper 

 thoracic region. It decreases very slightly down to the 

 middle of the thoracic region. From here downward it in- 

 creases gradually until it is over 6 cm. wide at the sacrum. 

 There is a gradual increase in the thickness of the centra. 

 The first thoracic centrum is 1.5 cm., the third lumbar cen- 

 trum is 2.7 cm. thick. The fourth and fifth lumbar centra 

 are about the thickness of the first and second. The 

 intervertebral discs correspond in width and thickness to the 

 centra. The disc between the first and second thoracic verte- 

 brae is only .5 cm. in thickness, while that between the third 

 and fourth lumbar vertebrae is 1.3 cm., in thickness. The 

 fourth and fifth lumbar discs are about the same thickness 

 as the first and second. When seen from the side (Plates 

 XXX and XXXI) the vertebral column is S-shaped. On 

 account of a slight kyphosis the convexity in the upper 

 thoracic region is a little greater than usual. For this same 

 reason the spinous processes of the first three thoracic verte- 

 brae are nearly horizontal. 



The sternum extends from the level of the upper part 

 of the third to the level of the lower part of the eleventh 

 thoracic vertebra. The sternal angle is at the level of the 

 lower border of the fourth thoracic vertebra. The gladiolus 

 extends from the lower border of the fourth to the middle 

 of the ninth thoracic vertebra. The xiphoid process is 



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