DYSTOKIA BY PELVIC CONSTRICTION. 



271 



are various. They may belong to the bones of this region, or to its con- 

 nective tissue ; and they always more or less diminish one or more of the 

 dimensions of the parturient canal, and offer an obstacle to the passage 

 of the fcEtus. These cases, however, are somewhat rare ; they are gen- 

 erally found to be due to complete deformity of the pelvis., exostoses., fractures ^ 

 or tumors. 



Complete Deformity of the Pelvis. 



As has been observed, complete deformity of the pelvis is very rare 

 among animals. When due to rachitism, it is most frequently noted in 

 the Pig. In this animal the pelvis is sometimes greatly distorted, and 

 not unfrequently there is accompanying deviation in the vertebral spine. 

 This condition is seldom seen in other creatures. 



Saint-Cyr informs us that in the Museum of the Lyons Veterinary 

 School, there is the pelvis of a Mare and another of a She-Ass, which 



Fig. 64. 

 Completely Defok.med Pelvis: Mare.. 



present a very remarkable degree of general constriction, and which must 

 have offered a very serious obstacle to parturition if the animals had ever 

 been pregnant. That of the Mare (Fig. 64) is singularly depressed on 

 both sides, the ischia, and especially the pubis, being atrophied with re- 

 spect to size. The oval foramina and cotyloid cavities are close together, 

 the floor of the pelvis is extremely contracted and angular, and the pu- 

 bic arch is hypertrophied. In this specimen there is a very notable 

 diminution in the different diameters of the pelvic cavity ; the supero-in- 

 ferior, instead of being about 8^'^ inches is only about 6, and the bi-iliac 

 diameter is but dt% instead of being 7^ to 8 inches. 



According to Saint-Cyr, the diagnosis of this deformity should not be 

 difficult, especially when it is so marked as in this instance. Vaginal ex- 

 plorations should soon discover it, and the diminution in size may be ap- 

 proximately determined by spreading the fingers, and in this way measur- 

 ing the two diameters. The diagnosis may not be so easy, however, 

 when the canal is partly or wholly occupied by the foetus. 



