THE UROGENITAL SYSTEM 157 



same place is selected and continuous pressure exerted to detect 

 a hard, irregularly moving mass in the uterus. 



Palpation of the uterus through the rectum or vagina is a 

 means of determining the existence of the fetus after the fifth 

 month. Before this time the fetus may be so small as to 

 escape detection, especially in large mares. Experience in 

 manipulating the genital organs is essential to the success of 

 this operation. 



Well toward the end of the gestation period the vulva swells 

 and the vaginal mucous membrane is greatly congested. Afew 

 hours before parturition the lips of the vulva are considerably 

 swollen and gape apart. The mare becomes restless, ceases to 

 eat, switches, lies down, rises, and the labor pains in due time 

 effect expulsion of the fetus. 



Subjective signs of pregnancy consist of those things that are 

 appreciable by the affected individual alone. Domestic animals 

 exhibit only a few of these signs. Pain produced by the violent 

 movements of the fetus is the most common; it causes the mare to 

 switch, bite at the flank, and kick at the belly. 



In 1913 Abderhalden perfected a test to determine the presence 

 or absence in the blood serum of ferments capable of digesting 

 placental albumins and believed to be produced only during preg- 

 nancy. It is not a test for pregnancy, but demonstrates certain 

 substances produced as a result of this condition. The test is 

 strictly a laboratory procedure and requires a careful, well- 

 trained technician for reliable results. Zell reports that he has 

 made nearly 400 tests with results that checked closely with other 

 tests. Blood samples drawn as early as the second and third 

 week after assumed conception were as satisfactory as those 

 drawn later. 



The effect of pregnancy is popularly supposed to be a serious 

 drain on the system, due to the fact that a large supply of nutri- 

 ents is essential for the development of the unborn young in the 

 uterus. Recent investigations indicate that pregnancy does not 

 exhaust the mother. In fact young pregnant animals grow 

 normally during this period without great additional increase in 

 food supply, one reason for this being that the fetal tissues are 

 largely composed of water. During the period of lactation, 

 however, growth may be interfered with or even stopped alto- 

 gether. The conclusion is that dwarfing in the young mother 

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