SURGERY AND OBSTETRICS 361 



Hoats in it. This fluid diminishes shock or injury to the fetus in 

 utero and also serves as a lubricant in the vaginal canal in parturi- 

 tion. The allantois is a double membrane, one portion being applied 

 to the internal aspect of the chorion and the other to the external 

 aspect of the amnion. The two membranes form a constrictor tube, 

 the urachus, which extends into the abdomen of the fetus through the 

 umbilical opening and thence to the anterior portion of the bladder 

 with which a communication is provided. Thus, the allantoic space 

 serves as a urinary reservoir. 



The umbilical cord is the means of communication between the fetus 

 and uterus. It is composed of embryonal connective tissue, which 

 supports the, urachus, arteries and veins. 



Parturition 



The symptoms of parturition consist of congestion and tumefac- 

 tion of the mucous membrane of the vulva and enlargement of the 

 mamm'cB. The primary symptom of parturition is restlessness, and 

 the sow will usually make a bed before she assumes the lying posture. 



The expulsion of the fetuses from the uterus is the result of the 

 combined muscular activity of the uterus and abdominal muscles. 

 Just prior to the time that the muscular contractions begin, in normal 

 animals, the cervix of the uterus relaxes and several fetuses will be 

 delivered in a relatively short time. If expulsion is delayed while the 

 fetus is in the vaginal canal the pig may be dead because of the 

 strangulation of the blood supply through the umbilical cord and the 

 cessation of respiration while the pig is in the canal. Such pigs may 

 be revived by cleaning the mouth and nostrils and by the institution 

 of artificial respiration which it may be necessary to continue sev- 

 eral minutes. 



DIFFICULT PARTURITION DYSTOCIA. 



Difficult parturition may be due to a variety of conditions, some 

 of which are known and may be overcome. Some of the conditions 

 that cause or are associated with dystocia are: the breeding of gilts 

 that are too young-; the mating of young gilts with old boars ; the mat- 

 ing of small frame sows with large coarse boars; allowing the sow to 

 become too fat; requiring insufficient exercise of pregnant sows; con- 

 stipation and impaction. In addition to the foregoing, dystocia is oc- 

 casionally the result of malformation of the pelvis or abnormality of 

 the musculature and cervix of the uterus. 



