OBSTETRICAL PHYSIOLOGY 



Reproduction. 



The specific function of the generative organs is the pro- 

 creation of the species, including conception, the intra-uterine 

 nutrition and development of the fetus, its expulsion after a cer- 

 tain degree of development and its further nutrition for a time 

 after birth by milk from the mammae, until the young has ac- 

 quired sufficient development to enable it to lead a wholly inde- 

 pendent existence. The two sexes in mammalia are normally 

 wholly distinct so that, before conception can take place, a con- 

 jugation of the male and female, coition or copulation, must oc- 

 cur. In all mammalia there are more or less apparent vestiges 

 of each part of the genital apparatus of the opposite sex in each 

 individual, but they naturally become arrested in their develop- 

 ment in the embryonic stage and remain wholly functionless ; 

 rarely do we meet with anomalies (hermaphrodites) in which the 

 analogous organs of both sexes develop more or less completely ; 

 less rarely we observe the development of some ' of the male or- 

 gans (testes) and others of the female (uterus and vagina) in one 

 individual. These animals partaking of a bisexual nature are, so 

 far as we have observed, uniformly sterile. In other instances 

 (freemartins), all genital organs may be arrested in the embry- 

 onic stage and the animal remain virtually asexual. 



Before reproduction becomes possible the breeding animal must 

 have reached the period of puberty or sexual maturity, the period 

 when ova and spermatozoa mature and are discharged and sexual 

 desire is established, up to which time the reproductive organs 

 are dormant in so far as their specific functions are concerned. 

 Puberty or sexual maturity occurs at varying ages in different 

 species, breeds and individuals. Much depends upon the food 

 supply and rapidity of growth. It quite uniformly occurs in both 

 sexes prior to the completion of growth. There seems to be a 

 tendency towards early puberty in short lived species and late in 

 those which normally have a long span, of life, but the rule is in- 

 constant. The normal duration of life in the cow is approxi- 

 mately twice that of the bitch, but the former tends to become 

 sexually mature at an earlier age than the latter. 

 40 



