DISEASES OF THE GENERATIVE ORGANS. 175 



that the work proceeds with redoubled energy to the complete expul- 

 sion. This is the reason why it is wrong to rupture the water bags if 

 the presentation is normal, as they furnish a soft^ unifomi pressure 

 for the preliminary dilation of the mouth of the womb and passages, 

 in anticipation of the severe strain put upon them as the solid body 

 of the calf passes. 



The cow often calves standing, in which case the navel string is 

 broken as the calf falls to the ground. If, however, she is recumbent, 

 this cord is torn through as she rises up. The aftei-pains come on 

 3 or 4 hours later and expel the membranes, which should never be 

 left longer than 24 hours. 



NATURAL PRESENTATION. 



When there is but one calf the natural presentation is that of the 

 fore feet with the front of the hoofs and knees turned upward toward 

 the tail of the dam and the nose lying between the knees. (PI. XV.) 

 If there are twins the natural position of the second is that of the 

 hind feet, the heels and hocks turned upward toward the cow's tail. 

 (PI. XVIII, fig. 1.) In both of these natural positions the curvature 

 of the body of the calf — the back arched upward — is the same with the 

 curv^ature of the passages, which descend anteriorly into the womb, 

 ascend over the brim of the pelvis^ and descend again toward the 

 external opening (^'ulva). Any presentation dift'ering from the 

 above is abnormal. 



OBSTACLES TO PARTURITION. 



With a well-foi-med cow and calf and a natural presentation as 

 above, calving is usually prompt and easy. Obstacles may, however, 

 come from failure of the mouth of the womb to dilate ; from twisting 

 of the neck of the womb ; from tumors in the vagina ; from dropsy in 

 the womb or abdomen ; fi-om over distension of the rectum or bladder; 

 from undue narrowing of the passages; from excess of fat in the walls 

 of the pelvis; from the disturbance of a ners'ous cow by noises; from 

 stone or urine in the bladder; from wrong presentation of the calf, 

 its back being turned downward or to one side in place of upward 

 toward the spine of the dam; from the bending backward into the 

 body of the w^omb of one or more limbs or of the head ; from presen- 

 tation of the back, shoulder, or croup, all four limbs being turned 

 back; from presentation of all four feet at once; from obstruction 

 caused by an extra head or extra limbs, or double body on the part of 

 the offspring (PI. XIX) : from dropsy or other disease of the calf; 

 from excessive or imperfect development of the calf ; from the impac- 

 tion of twins at the same time into the passages; or it may be at 

 times from the mere excessive volume of the fetus. 



