TRUNK OF THE FOETUS. 173 



Greater Pelvis. 



- In the superior opening of the greater pelvis, we distinguish 

 but two diameters, both transverse. The posterior extended 

 from the middle of one iliac crest to the other, eleven mches. 

 The anterior, between the two anterior superior spinous processes 

 of the ilium, ten inches. From the middle of the iliac crest, to 

 the superior strait, three and a half inches. From the middle 

 of the iliac crest to the tuberosity of the ischium, (whole depth 

 of the pelvis) seven and a half inches nearly.* 



Lesser Pelvis. 



Superior Strait, sometimes called ab- Inferior Strait, or perineaL 



dominal. 



Inches. Inches. 



Antero-posUrior diameter, from Antero-posterior diameter, be- 



the symphysis of the pubis to the tween the symphysis pubis andS 



promontory of the sacrum, - - 4 front of the coccyx, which may be 

 Transverse, or iliac, which increased near an inch by the mo- 



crosses the former, at a right bility of the coccyx backwards, 4 



angle, ------ 5 Transverse, or ischiatic, from 



Oblique, from the acetabulum of one tuberosity of the ischium to 



one side, to the sacro-iliac, articu- the other, ----- 4 



Lation of the other, - - - 4.J. Oblique, from the tuberosity of 



the ischium of one side, to the mid- 

 dle of the great sacro sciatic liga- 

 ment of the other, nearly 4 



The height of the posterior wall of the lesser pelvis, 

 formed by the sacrum and coccyx, (of which the 



latter forms an inch,) is nearly - - 5 inches. 



Height of the anterior wall formed by the os pubis, 1| " 



Height of the lateral walls, - - 3J " 



Thickness of the symphysis pubis, about - \ " 



Depth or sine of the cavity of the sacrum,f nearly - I " 



The Trunk of the Fcstus. 

 At birth, each vertebra consists of three pieces, connected by 



* The depth or length of the pelvis is rather greater in the male than in the 

 female. 



f Dimensions of the child's head at birth. The long diameter, from the 

 vertex or posterior extremity of the sagittal suture to the chin, 5 1-4 inches ; 

 antero- posterior, from the middle of the frontal bone to the tubercle of the 

 occipital, 4 inches; transverse, from one parietal protuberance to the other, 

 3 1-2 inches. 



15* 



