PATHOLOGY OF PREGNANCY AND PARTURITION 439 



than those of woman. The course of labour in mares is rendered 

 much easier by the fact that the only important structure closing 

 in the pelvis is the broad pelvic fascia. In cows the mobility of 

 the sacro-iliac joint and the sacro-lumbar joint is greater than in 

 mares. Labour in sheep and goats is still easier owing to the 

 mobility of the upper sacral vertebrae, which renders possible a 

 considerable widening of the pelvic outlet. In swine difficult 

 labour is very rare, owing to the marked concavity of the sacrum 

 and the extreme mobility of the sacro-lumbar and the sacro-iliac 

 joints. In bitches the false pelvis is more capacious than in 

 any other domestic animal, and the sacro-iliac joint is so mov- 

 able as to form a regular diarthrosis. In addition to the 



FIG. 212. Robert's pelvis. (Spath.) 



FIG. 213. Naegele's pelvis. (Spath.) 



anatomical advantage enjoyed by domestic animals, there is 

 the fact that pathological changes in the pelvis, causing a diminu- 

 tion of the pelvic diameters, are much less common. Franck 

 indeed states that a narrow pelvis in adult animals only exists 

 in a relative sense when the young one or the foetal head, that 

 is to say, is disproportionately large. The only pelvic deformities 

 with which he is acquainted are those due to fracture of the 

 pelvic bones, exostosis and ankylosis of the joints, such as the 

 sacro-iliac, whereby a pelvis similar to Robert's pelvis may be 

 formed in animals. 



As we have seen, primitive peoples do not reckon a con- 

 tracted pelvis among the hindrances to parturition. According 

 to the universal testimony of experienced and expert travellers, 



