146 A TREATISE ON HORSE-BREEDING. 



tion. As a rule the disused generative organs fail to acquire 

 that permanent development which attends on habitual im- 

 pregnation; and even after a single conception a long period 

 of non-breeding leads to a striking diminution of the womb 

 and passages. 



But difficulty is often experienced in securing the impreg- 

 nation of heifers that have reached full maturity but are 

 neither old nor hard-worked, and the same difficulty is met 

 with in comparatively young and idle mares. In such cases 

 the trouble may often depend on undue sexual excitement, 

 which leads to a spasmodic and rigid closure of the neck 

 of the womb during copulation or to excessive expulsive con- 

 tractions of that organ and the vagina and the rejection of 

 the semen before impregnation has been effected. 



Another occasional cause of sterility in such cases is the 

 degeneration of the fallopian tubes, which have become 

 blocked by the. abnormal fatty product and no longer allow 

 of the descent and impregnation of the ovum. 



The obvious preventive of these conditions is to maintain 

 the functional activity of the organs from the time of full 

 maturity onward. It is a fundamental law of organic nature 

 that structures and functions are developed in ratio with 

 their use, so long as this is kept within natural bounds, and 

 the generative system is no exception to this law. The cow 

 or mare that is bred every year is a more certain breeder 

 than the one which is allowed to skip three or four years 

 between successive conceptions. The faulty^ conditions re- 

 sulting from this deferred or irregular breeding will be in- 

 dividually considered below. 



There is not a Scylla but has its Charybdis. We should 

 keep this in mind in avoiding the danger just mentioned, and 

 not be driven to the opposite extreme of breeding from very 

 young females, whose development and stamina will be im- 

 paired by the constant drain upon it for the nourishment of 

 the coming progeny. It is notorious that females who breed 

 too early fail to attain the full size and development of their 

 family. * * * Females should not be put to the male 

 until they are at least verging on maturity. Above all, the 

 system of breeding from very immature animals should not 



