132 OBSTETRICAL PHYSIOLOGY. 



which they reach their apogee. Its contractility, which signifies also 

 its retractility, enables it to contract on itself after delivery, and to 

 nearly obliterate its cavity. This rapid diminution in the capacity 

 of the organ closes the orifices of the vessels which open on its internal 

 surface during the act, and thus prevents fatal haemorrhage. 



Its main function, however, appears to be concerned in the expul- 

 sion of the foetus, and then, as at other times, it is entirely independent 

 of the will. Besides, the intensity of the contractions is not always 

 related to the strength of the animal ; pain deadens and paralyses 

 the contractile force, as is seen in primiparous creatures. "When the 

 contractions have been vigorous, the uterus rapidly diminishes ; but if 

 they have been slow and weak, the organ slowly contracts on itself. 

 When it does not contract quickly after delivery it is said to be inert, 

 and the cause is to be found in the expenditure of its contractile power, 

 either through excessive distension, a delivery too prompt or too slow, 

 or general weakness of the maternal system. By prolonged exertion, 

 like the voluntary muscles, those of the uterus become weakened ; so 

 that when the act of parturition has been protracted, the contractions 

 of the organ become slow and feeble, or cease altogether. Opiates and 

 narcotics generally produce the same effect, and are therefore success- 

 fully administered when the contractions are too energetic or painful 

 during delivery or before abortion. The contractions are stimulated by 

 irritation of the cervix or body of the uterus — such as is produced by 

 retention of the whole or a portion of the placenta, titillation of the 

 cervix by the finger, frictions on the belly, the application of cold to 

 this part, or the administration of ergot of rye. 



Form. 



The uterus, after conception, begins to change in form as well as in 

 volume and structure ; this alteration, like the others, proceeds pari 

 passu with the development of the fojtus. The body becomes round, 

 and in the Carnivora, as already described, the cornua elongate and 

 show the alternate dilatations and constrictions due to the presence of 

 the young in their cavities. In the Mare, Cow, and Sheep, if there is 

 but one foetus, a single horn is enlarged — usually the right — to contain 

 the posterior limbs, while the other is relativelj" smaller and contracted, 

 and looks a mere appendage. When a Carnivorous animal contains 

 only one foetus, it is developed in the horn, and not in the body of the 

 uterus, and it is not until parturition commences that it descends into 

 the latter ; should the creature die before delivery, the offspring will be 

 found there. In this species each horn generally contains one or more 

 young ; should there be only two, one occupies each cavity ; but when 

 there is only one foetus, it is then in one of the cornua. 



The changes taking place in the cervix of the uterus during pregnancy 

 have not been accurately ascertained in the domesticated animals, as in 

 the smaller species there is usually no occasion or necessity to make an 

 examination ; while in the larger the risk of injury to the examiner, and 

 of abortion in the animal, militates against such an investigation. It is 

 only known as a fact, that it widens at the termination of gestation, and 

 loses its cervical character, as well as its longitudinal mucous folds. It 

 may also be noted that, from being firm and dense at ordinary times, 

 its texture becomes gradually soft and elastic ; while it diminishes in 

 length, its projection into the vaginal cavity is lessened, and indeed at 

 a late period almost effaced, it appearing merely as a kind of ring. 



