Notes on the proportion of the sexes in dogs / by Walter Heape.

  • Heape, Walter, 1855-1929.
Date:
[1907]
Catalogue details

Licence: In copyright

Credit: Notes on the proportion of the sexes in dogs / by Walter Heape. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    25/32 (page 145)
    This breed then is specially adapted for checking the general result given above and I have set it forth in Table IX. Table IX. Schedule Returns. Bloodhounds, gestation and sex of pups. Days of gestation Dogs per 100 bitches Litters Pups per litter (1) 53—61 125-64 9 97 (2) 62—65 138-46 9 6-8 (3) 66—69 157-14 4 9-0 Here is a very striking confirmation of the view advanced. The returns of the pups per litter in Tables VIII and IX do not indicate that the size of the litter has anything to do with prolonged gestation; the litters produced both in divisions (1) and (3) in each of these tables are bigger thau those in division (2), the normal gestation period, so it does seem as if the excess of male embryos in the uterus is directly responsible for the delay in parturition. I do not of course maintain that the length of gestation has any influence whatever on the sex of the young born, these results only show the tendency to prolong gestation when an excess of male embryos are present in the uterus. The association of a longer gestation period with the produc- tion of an excess of males may be regarded as evidence either that male embryos require a longer uterine life for their full development or that they are born, when possible, in a more advanced condition than the females. This is a question of considerable interest in relation to the physiology of breeding, and also regarding various sexual differentiations. Another point of interest with regard to Table VIII is that whereas 20 litters of Large dogs (18 35 °/0 of the whole) and 49 litters of Terriers (29 °/0) have a shorter gestation than normal, 8 litters of Large dogs (7,34°/0), and 7 litters of Terriers (4-14°/0) experience a longer gestation than normal. Thus, while on the one hand abnormally short gestation is more usual than abnormally long gestation for both classes of dog, the proportion of Terriers is greater than that of Large dogs for short gestation, and the proportion of Large dogs greater than that of Terriers for long gestation periods.