520 Veterhiary Obstetrics 



which she selects for her nest, she will gather all the herbage in 

 an ever widening circle and carry it to the central spot, where 

 she deposits it in the form of a mound, until she has acquired 

 sufficient to suit her purposes. We have seen such mounds as 

 extensive as four or five feet in diameter and two or three feet in 

 depth. Into the center of this mound she crawls in such a way 

 as to become almost or quite hidden and there gives birth to her 

 young. In confinement, she builds such a nest as her environ- 

 ment makes possible or demands, and it may vary in every degree 

 from that which we have already described to no bed at all in 

 some cases where she is denied the proper material for its con- 

 struction. Increased domestication brings decreased instinct in 

 preparing such bed. 



The rabbit constructs a burrow and pulls from her own body a 

 sufficient amount of fur to line a very complete and cozy nest in 

 which to give birth to her very immature young. 



Exploration of the genital passages just prior to labor reveals 

 the fact that the cervix of the uterus has largely disappeared, 

 and there simply remains a brief constriction at the os uteri ex- 

 ternum. The OS may be .somewhat open, so that the fingers can 

 readily be introduced into the uterine cavity and come in contact 

 with the smooth surface of the chorion over the small area 

 where no placental tufts exist. As labor progresses, the os uteri 

 gradually dilates and, when the contractions of the uterine walls 

 become more pronounced, the dilation of the os uteri externum 

 rapidly increases, until it finally becomes wholly effaced and the 

 uterine cavity continuous with that of the vagina. 



When the os uteri has become sufficiently dilated, the water- 

 bag passes into and through the opening and portions of the 

 fetus .soon advance into the os uteri and vagina and the definite 

 symptoms of labor quickly become established. The uterine 

 contractions now begin in earnest and are soon accompanied by 

 contractions of the abdomen and diaphragm. The animal shows 

 well marked pain and suffering. Depending somewhat upon 

 species, the animal shows a tendency to lie down and rise fre- 

 quently, and in general to show abdominal pain. The mare 

 may paw with the fore feet and strike at the abdomen with 

 the hind feet. The animal ceases to feed and shows much 

 anxiety, which is indicated to some extent by a disturbance of 

 the circulation, con.si.sting chiefly in an increased pulse rate. In 



