THE PELVIC CANAL 49 



latter the conjugatareprfisents the short diameter of the pelvic 

 inlet. The greatest width of the pelvis is called by Franok the 

 middle transverse diameter, or distantia psoadica, Franck 

 recognizing besides an inferior transverse diameter extending 

 between the pectineal tubercules. This diameter is about 

 2 cm. shorter than the greatest width of the pelvis. 



The height of the pelvic inlet (anterior vertical diameter 

 of Franck, diameter sacro-pubien of St. Cyr and Violet) is 

 formed by a line resting vertically upon the anterior extremity 

 of the ischio-pubic symphysis. This line in the cow touches 

 the body of the third sacral vertebra (Fig. 11). On account of 

 the concavity of the inferior face of the sacrum, this diameter 

 is of considerable size in bovines. In the same manner as in 

 the inlet, we distinguish length and width of the pelvic 

 passage. The first or vertical diameter of this passage rests 

 vertically upon the deepest point of the symphysis, and 

 touches the body of the second coccygeal vertebra. The 

 width represents the distance between the cotyloid cavities 

 (the middle transverse diameter of Franck). It is of little 

 value to define the diameters of the outlet on account of its 

 expansibility ; only the distance between the postero-external 

 angles of the ischium are unchangeable. 



The pelvic axis, also termed line of guidance, is a line 

 which the long axis of the foetus follows during parturition 

 (Fig. 12). This line is very important, as its course indicates 

 in which direction traction should assist the expulsive force. 

 This line is obtained by uniting the centres of all lines vertical 

 to the symphysis and which come in contact with the inferior 

 surface of the sacrum and the first coccygeal vertebra. This 

 line runs obliquely upwards at the inlet, descends a little to 

 about one-half of the symphysis, and now ascends toward 

 the outlet, forming with a horizontal pelvic plane an angle 

 of 45°. 



ESTIMATION OP PELVIC DIMENSIONS — PELVIMETRY. 



Pelvic dimensions during life can be ascertained with a 

 great deal of accuracy. There are two methods: one by C. 



