I40 OBSTETRICAL PHYSIOLOGY. 



we have the researches of Baumeister and Rueff ; from these it appears 

 that, with pure-bred Persian Mares, the gestation period was 341 days — 

 343 for male foals, and -^t,^ for females ; in thorough-bred Arab Mares, 

 the average was 338 days — 339 for males 337 for females ; in high-bred 

 Russian Mares, some of which belonged to the Orloff race, the average 

 duration was 3415^ days — 341 for males and 342 for females. With 

 English Mares, they found that in half-breeds the average was3395^ days 

 — 340 for males, and 339 for females. 



Saint-Cyr, referring more particularly to Gayot's observations, arrives 

 at the following conclusions : 



1. That in the Mare, the normal duration of pregnancy may be fixed 

 between 340 to 350 days — this being the interval in which the majority 

 of foals are born. 



2. Some foals may be born alive from the 300th to the 310th day, but 

 this is rare. 



3. Births are frequent between 325 and 340 days • 



4. They are not rare from 350 to 365 days, but they are indeed so 

 after the latter period. 



5. We may consider 300 to 400 days as the extreme limits within which 

 normal gestation occurs in the Mare ; below or beyond these it ceases to 

 be natural and really physiological. 



6. According jto the researches of M. Gayot, pregnancy is often a 

 little longer for a colt than a filly ; and though this conclusion is certain- 

 ly not founded on a sufficiently large number of observations, it never- 

 theless acquires a certain degree of probability from being in conformity 

 with what is observed in the bovine species. 



It is also generally admitted that pregnancy is longer in the Ass than 

 the equine species. 



The average duration of pregnancy with thirty-three thorough-bred 

 Mares which foaled at the celebrated Middle Park Stud, Eltham, in 

 1876, I find on examination to be 335^ days — the shortest periods being 

 316 days (one intance), and 318 days (one instance) ; and the longest 

 354 days (one instance), and 348 days (one instance). Between the 

 320th and 330th days there were only 5 instances ; between the 330th 

 and 340th days there were 1 1 instances ; and between the 340th and 

 348th days there were 15 instances. Owing to some of the Mares having 

 been put to the Horse more than once, and in some cases at intervals of 

 several days, the averages may not be absolutely correct, as the last 

 coitus has been the one which is reckoned from. But with one Mare 

 (Entremet) put only once to the stallion (Rosicrucian), the period was 

 324 days ; with another (Hilda) put to the same stallion, the period was 

 332 days ; and with another (Imogene) and this stallion, it was 342 days. 



With regard to sex, there were sixteen colts and seventeen fillies : the 

 average gestation period of the former was 3363^ days, and the latter 

 334 days. The shortest period (316 and 318 days) was with fillies, and 

 the longest period was also with fillies (354 and 348 days). The ages of 

 the Mares ranged from five to nineteen years ; there being three at five, 

 two at six, three at seven, two at nine, two at ten, six at twelve, four at 

 fourteen, four at fifteen, two at sixteen, one at seventeen, one at 

 eighteen, and three at nineteen. In the first group, pregnancy averaged 

 340 days; in the second 350^ days; in the third 328^^ days; in the 

 fourth 34054 days ; in the fifth 336 days ; in the sixth 337 -^ days ; in 

 the seventh 336)^ ; in the eighth t^t^t, days ; in the ninth 340^ days ; in 



