The Position of the Fetus in the Uterus. 38 1 



abdominal floor at a verj^ earl}- period in pregnancy, the question 

 of the inclination of the uterus can have less influence upon the 

 direction in which the head-end shall present than in the uni- 

 para, and so we find that they present somewhat indifferently 

 though the tendency for the head-end of the fetus to present 

 toward the vulva is still well marked. 



Late in gestation, the hinder parts of the fetus become more 

 developed, so that in the larger herbivora these parts equal or 

 exceed in bulk and weight the anterior portions of the bod}-. 

 By this time the uterus is lying upon the abdominal floor and 

 the posterior part of the fetus occupies the lowest point of the 

 abdomen in the neighborhood of the diaphragm. In addition to 

 this, the fetus has acquired a longitudinal diameter which is 

 in excess of the transverse diameter of the uterine cavity, and 

 the relationship between the long axis of the fetus and that of 

 the uterine cavity becomes fixed and permanent. 



We thus find that, in the vast majority of cases in our larger 

 domestic animals, the fetuses regularly present anteriorly at the 

 time of birth. In multiparous animals, the fetuses present some- 

 what indifferently, usually anteriorly, frequently posteriorly. 



The relationship between the transverse axis of the fetus and 

 that of the maternal body is largely determined by the form of the 

 fetus itself and of the surface upon which it rests. We have alread}- 

 learned that the fetus early assumes the form of an arc and that this 

 form is maintained throughout its intra-uterine life. The fetus 

 bends ventral wards and its form inhibits any marked dorsal flexion. 

 During the early stages of gestation, the uterus is suspended by 

 its ligaments in the abdominal cavity and its cornua in the mare 

 are more or less curved downward at their middle portion. In 

 ruminants the gravid cornu or cornua retain for a time their non- 

 gravid .spiral form, curving downwards, backwards and then 

 upwards. An arciform fetus would normally assume the most 

 stable position, which would be with its convex or dorsal surface 

 applied to the convex side of the uterus and its concave or ven- 

 tral surface toward the concave uterine surface. 



At this stage the natural position of the fetus in the mare is with 

 its dorsum downward and its ventral surface upward. In the 

 ruminant, so long as the uterus remains in its non-gravid position, 

 the ventral surface of the fetus would normally present down- 



