CHAPTER XIX. 



parturition and the Diseases Incidental Cbereto. 



Normal parturition is the act of expulsion of the foetus 

 from the womb of its mother after the completion of its full 

 period of development within that organ. 



The period elapsing from the time of its first conception and 

 its final expulsion from the uterus is called the term or period of 

 gestation. This, as it occiirs in sheep, extends over a period of 

 nearly five months, or, to be more exact, from 142 to 150 days. 



The act of parturition, while a natural physiological process, 

 is attended in all mammalia with more or less pain and risk to 

 the existence of the subject. The foetus, being fully developed, 

 acts' as an irritant to the organ in which it has been elaborated, 

 inducing a marked disturbance of the nervous system, accom- 

 panied with violent contractions of the womb, aiming to expel 

 that which has now become a foreign body. 



Expulsion is not effected by one effort, but by successive, 

 slow and progressive contractions, becoming more severe and ex- 

 hausting as the labor becomes prolonged. At first the pains are 

 of short duration, increasing gradually in force. Normal con- 

 tractions take place at the fundus, (center of the body of the 

 womb); the cornua (horns) shorten towards the fundus; the 

 womb towards the neck, and the neck towards the opening into 

 the vaginal cavity called the os. The water^bag enveloping the 

 foetus acts as a mechanical dilator to the neck of the womb, 

 which, as the pressure increases, becomes thinner and shorter, 

 periaiitting the water-bag to dilate its opening or os. The limb* 

 and head of the foetus acting as a wedge maintain the dilatation 

 of the parts, which, as the pains increase in severity, finally f ti- 



