22 LIVE-STOCK JUDGING 



fore legs in such a way as to form a conical protrusion. 

 This helps in the dilation of the parts involved as the con- 

 tractions of labor gradually cause the expulsion of the 

 foetus. Not only do the structures of the dam favor this 

 expulsion by their relaxation, but the suppleness and 

 flexibility of the foetus itself materially assists. The head, 

 at this age, is capable of considerable compression and 

 alteration in form to accommodate itself to the restricted 

 passage through which it is forced, while the chest may 

 have its vertical dimension flattened by the bending back- 

 ward of the spinous processes of the thoracic vertebrae, to 

 which this dimension of the chest is largely due. In the 

 case of multiple births, as in the sow, considerable time 

 may elapse, with apparently complete cessation of labor, 

 between the expulsion of each foetus. 



27. Lactation. — There is naturally a distinct correla- 

 tion between reproduction and lactation. As pregnancy 

 advances lactation diminishes, if the female is milking at 

 the time, accompanied by a corresponding increase in 

 weight due to the deposition of fat, in addition to the 

 growth of the foetus. Some females cannot become preg- 

 nant while suckling young. There is usually a complete 

 cessation of lactation for a period prior to parturition, 

 although some cows will milk persistently for years and 

 can hardly be dried off, though calving regularly. With 

 the approach of parturition the udder manifests a return 

 of functional activity, " springing," as we say, indicating 

 the increase in size and fullness of form most marked in 

 females pregnant for the first time. Such udders finally 

 secrete a characteristic waxy material, and finally milk, a 

 few days or hours before parturition. After the birth of 

 the foetus, the expulsion of the membranes constituting the 

 afterbirth and the ultimate contraction of the uterus, the 



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