Maternal Organs of Reproduction in Animals. 



259 



cow forty, the ewe twenty-two, the bitch nine, and the sow 

 sixteen weeks. It certainly is a remarkable fact, and one which 

 shows the mighty power of the allwise Creator, that, in animals 

 placed so high in the scale of organised beings as the canine 

 race, full and perfect development of their young should be 

 effected in the short space of sixty-three days. If, however, we 

 descend the scale, we shall find that this is comparatively a 

 long period to be occupied in the perfecting of the offspring of 

 the lower animals. 



The late and much lamented Earl Spencer has recorded in the 

 pages of your Journal* his observations on the duration of gesta- 

 tion in no less than 764 cows ; and we are much gratified in being 

 able to say that he has thereby rendered most efficient aid to 

 science, as well as considerable service to the practical breeders 

 of cattle. I refer to the table accompanying the paper for full 

 details, but I shall nevertheless make an extract or two in con- 

 sequence of the important bearing these statements have on this 

 part of our subject : — £f From the inspection of this table," his 

 Lordship says, " it will be seen that the shortest period of 

 gestation, when a live calf was produced, was 220 days. Any 

 calf produced at an earlier period than 260 days must be con- 

 sidered decidedly premature, and any period of gestation exceed- 

 ing 300 days must also be considered irregular, but in this latter 

 case the health of the produce is not affected. It will also be 

 seen that 314 cows calved before the 284th day, and 310 calved 

 after the 285th ; so that the probable period of gestation ought 

 to be considered 284 or 285 days, and not 270, as stated in the 

 book upon Cattle, published under the superintendence of the 

 Society for the Diffusion of Useful Knowledge." 



The facts here mentioned with reference to the great differ- 

 ences in the time of gestation cannot, even in the present ad- 

 vanced state of science, be satisfactorily accounted for. Dr. Car- 

 penter, writing on the same subject, remarks that " the average 

 length of time which elapses between conception and parturition 

 in the human female appears to be 280 days or 40 weeks. 

 There can be little doubt, however, that gestation may be occa- 

 sionally prolonged for one, two, or even three weeks beyond that 

 period ; such prolongation not being at all unfrequent among the 

 lower animals, and numerous well authenticated instances of it, 

 in the human female, being on record. Upon what circum- 

 stances this departure from the usual rule is dependent has not 

 yet been ascertained ; but it is a remarkable circumstance, ascer- 

 tained by the observations of cattle breeders, that the male has 

 an influence upon the length of gestation — a large proportion of 



* Vol. i., p. 1G5, et seq. 



s 2 



