28 THE BREEDING OF ANIMALS 



28. The uterus. The uterus is a muscular sac con- 

 necting the Fallopian tubes and the vagina in which the 

 development of the fertilized egg is carried forward until 

 expelled from the body of the mother at the time of par- 

 turition (Figs. 8, 9, 10). 



In many mammals the uterus divides into two tubes 

 called horns. Each horn is connected with the corre- 

 sponding ovary by means of the Fallopian tube. 



The portion of the uterus nearest the vagina is some- 

 what constricted to form the cervix or neck of the uterus. 

 The vagina connects the uterus with the external genitals 

 called the vulva. 



29. The mammary glands. The possession of mam- 

 mary glands whose function is the elaboration of food 

 materials for the young offspring is characteristic of 

 all mammals. These glands are highly developed and 

 functional in the fertile female, but are also present in 

 rudimentary form in the male. In rare cases the rudi- 

 mentary glands present in the male have been known 

 to function. Hay ward at the Delaware Experiment 

 Station reports the case of a registered Guernsey bull 

 owned by that institution whose mammary glands 

 were developed to the extent of producing a small 

 amount of milk. Milk has also been produced from 

 the rudimentary mammary glands of male goats and 

 sheep. In man the rudimentaries of males have pro- 

 duced milk at birth and at puberty and in exceptional 

 cases at other times. The number of nipples in a 

 species bears some relation to the normal number of 

 young produced in a litter, and also to the needs of 

 the young animal. The glands are generally arranged 

 in pairs either along the ventral side of the thorax or 

 abdomen. 



