OBSTETRIC ANATOMY 



Each organ or part of the body contributes directly or indi- 

 rectl3' toward the function of reproduction, but. in many of them, 

 the influence is so remote that their relationship to breeding does 

 not require special consideration, while some organs or parts, de- 

 signed primarily to serve other ends, incidentally perform impor- 

 tant accessor}^ offices in the act of birth, as in the case of the pel- 

 vis, while other organs, like the ovaries, uterus, vagina, vulva and 

 mammae are devoted exclusively to the procreation of the spe- 

 cies and are designated reproductory or generative organs. 



A. The Accessory Organs of Reproduction. 

 The Pelvis. 



The pelvis constitutes an accessory organ of generation of 

 fundamental importance because the fetus must traverse its canal 

 in the process of birth, and success or failure may be decided by 

 the amplitude of the pelvic channel in relation to the size of the 

 fetal body. 



It consists of a bony girdle forming the posterior bod}^ wall, 

 into which extends the posterior prolongation of the peritoneal 

 cavity, and the terminal portions of the digestive, urinary and 

 generative systems. Our chief obstetric interest in the pelvis is 

 in its internal face , constituting the walls of its cavity. 



The pelvis is composed of the sacrum and coxae or ossa inno- 

 minata , with their ligaments, and the first two or three coccy- 

 geal vertebrae may be regarded as participating somewhat in its 

 formation as they constitute a part of the pelvic roof. 



The sacrum consists of a series of anchylosed .sacral yerte^ 

 brae , varying in number in the different species of domestic ani- 

 mals ; in the horse and ruminants five, in the pig four, and in 

 carnivora three. 



In sagitttal .section it presents the form of a truncated cone 

 with its base articulating anteriorly with the last lumbar verte- 

 bra and its apex posteriorly with the first coccygeal bone, 



In cross section it is triangular, with its base inferior. The 

 lateral surfaces offer roughened facets for articulation with the 

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