710 OF REPRODUCTION. 



in which the period of Conception could be fixed from peculiar circumstances, 

 with something like certainty. The mode of reckoning customary among 

 women, is to date from the middle of the month after the last appearance of 

 the Catamenia; but it is certain that Conception is much more likely to take 

 place soon after they have ceased to flow, or even before their access, than at 

 a later period ( 909) ; so that, in most instances, it would be most correct to 

 expect Labour at forty weeks and a few days after the last recurrence of the 

 Menses. The period of Quickening may be relied on in some women, in 

 whom it occurs with great regularity in a certain week of Pregnancy; but 

 there is in general great latitude as to the time of its occurrence. The usual 

 or average time is probably about the 18th week. 



931. The question of the extreme limits of Gestation, is one of great import- 

 ance both to the Practitioner and to the Medical Jurist ; but it is one which 

 cannot yet be regarded as satisfactorily decided. Many persons, whose expe- 

 rience should give much weight to their opinion, maintain that the regular 

 period of 40 weeks is never extended for more than two or three days ; whilst, 

 on the other hand, there are numerous cases on record, which, if testimony is 

 to be believed at all, (and in many of these, the character and circumstances 

 of the parties placed them above suspicion,) furnish ample evidence that Ges- 

 tation may be prolonged for at least three weeks beyond the regular term.* 

 The English law fixes no precise limit ; and the decisions which have been 

 given in our courts, when questions of this kind have been raised, have been 

 mostly formed upon the collateral circumstances. The law of France pro- 

 vides that the legitimacy of a child born within 300 days after the death or 

 departure of the husband, shall not be questioned ; and a child born after more 

 than 300 days is not declared a bastard, but its legitimacy may be contested. 

 By the Scotch law, a child is not declared a bastard, unless born after the 

 tenth month from the death or departure of the husband. 



a. The analogical evidence drawn from observations on the lower animals is extremely 

 strong. The observations of Tessier, which were continued during a period of forty years, 

 with every precaution against inaccuracy, have furnished a body of results, which seems 

 quite decisive. In the Cow, the ordinary period of gestation is about the same as in the 

 Human female; but out of 577 individuals, no less than 20 calved beyond the 298th day, and 

 of these, some went on to the 321st, making an excess of nearly six weeks. Of 447 Mares, 

 whose natural period of gestation is about 335 days, 42 foaled between the 359th and the 419th 

 day, the greatest protraction being thus 84 days, or just one-fourth of the usual term. Of 912 

 Sheep, whose natural period is about 151 days, 96 yeaned beyond the 153d day; and of 

 these, 7 \vent on until the 157th day, making an excess of 6 days. Of 161 Rabbits, whose 

 natural period is about 30 days, no fewer than 25 littered between the 32d and 35th; the 

 greatest protraction was here one-sixth of the whole period, and the proportion in which 

 there was a manifest prolongation was also nearly one-sixth of the total number of indi- 

 viduals. In the incubation of the common Hen, Tessier found that there was not unfre- 

 quently a prolongation to the amount of three days, or one-seventh of the whole period. 



b. In regard to Cows, the observations of Tessier have been recently confirmed by those 

 of Earl Silencer, who has publishedf a table of the period of gestation as observed in 764 

 individuals; lie considers the average period to be 284 or 285 days: but no fewer than 310 

 calved after the 285th day: and of these, 3 went on to the 300th day, and 1 to the 313th. 

 It is curious that, among the calves born between the 290th and 300th days, there was a 

 decided preponderance of males, these being 74, to 32 females; whilst all of those born 

 after the 300th day were fc'inales. 



c. It appears, however, from some recent statements published on the authority of Earl 

 Spencer, that the Male parent may exert an important influence on Ihe period of gestation. 

 Of 75 Cows in calf by a particular bull, the average period was 288^ days, or four days 

 more than the usual period. Ol'ihe 764 cows previously mentioned, 185 (nearly one-fourth) 

 went less than 281 days; whilst not one of the cows in calf to this bull did so. On the 



* A good collection of such cases will be found in Dr. Montgomery's excellent work on 

 the Signs of Pregnancy. 



f Journal of the English Agricultural Society, 1S39. 



