STERILITY AND SIGNS OF PREGNANCY 331 



"Sterility and infecundity in cattle may be due to a 



variety of causes, some of which are irremediable disease 

 of the ovaries, for instance. Others are capable of being 

 combated when their presence is ascertained. The most 

 common forms of the latter are stricture of the os uteri (the 

 passage leading from the vagina to the womb) and infectious 

 abortion. Stricture ought always to be looked for when diffi- 

 culty is experienced in getting a cow in calf, and the examina- 

 tion made when the cow is bulling. The hand and arm, well 

 greased, is introduced into the depths of the vagina and the 

 entrance to the uterus examined. Under normal conditions 

 the ringers can be admitted into the canal, but when it is con- 

 stricted a quill pen could not be passed, and fertilisation is 

 then impossible. In very many cases the employment of a 

 large probe at first, followed by the finger, a good deal of force 

 being often needed, is sufficient to ensure dilatation. It may 

 be necessary to use a dilator, or in some cases to incise the 

 walls of the os before the stricture can be removed. The 

 success attributed to insemination is frequently due to the 

 fact that manipulation of the os has caused its dilatation 

 before or during the use of the inseminator." 



" Great difficulty is often experienced in getting cows to 

 breed after they have been affected with contagious abortion. 

 It has been suggested that this is due to an acid condition of 

 the vaginal mucous membrane, and hence injections of a dilute 

 solution of bicarbonate of soda are recommended. Solution 

 of perchloride of mercury, ten grains to a quart of tepid water, 

 injected into the uterus and also into the sheath of the bull a 

 few days before copulation is perhaps the best treatment for 

 this form of the trouble, which is no doubt associated with 

 changes resulting from the action of the microbes to which 

 epizootic abortion is due." WM. R. DAVIS. 



The usual period of gestation is, in round figures, nine 

 calendar months. Lord Spencer's table (see R.A.S.E. 

 Journal, 1838) establishes the average period for healthy 

 cows at 280 days. 



Signs of Pregnancy. i. A cow does not come in season 

 when pregnant, otherwise she should do so at intervals of 

 about three weeks. 1 The exceptions to this rule are, that 



1 In summer, oestrum returns about the nineteenth day ; in winter, its 

 recurrence is slower by twenty-four or even forty-eight hours. 



