FERTILITY 649 



mares. Another method is to collect the semen in gelatine capsules 

 which are placed in the vagina before coitus, and then, when they 

 have been filled, to close their lids and insert them in the interior 

 of the uterus, where the heat of the body gradually melts the 

 gelatine and sets free the spermatozoa, By such means as this 

 several mares may be impregnated as a result of one service by a 

 stallion. In some cases pieces of sponge have been employed instead 

 of gelatine capsules.^ 



Artificial insemination has been of considerable use also in 

 remedying sterility in cows as well as in dogs.^ 



Several investigators by employing artificial insemination have 

 been successful in getting crosses between animals belonging to 

 varieties in which the disparity in size is so great that coitus 

 between them is difficult or impossible. Thus, Plonnis^ in 1876 

 successfully inseminated a lap-dog with the semen of a setter, and 

 obtained a pup which in most of its points resembled its father. 

 AUbrecht* performed a similar experiment and obtained a similar 

 result. More recently Heaps ^ has described some experiments 

 carried out by Millais, in which bloodhounds were inseminated with 

 spermatozoa obtained from Basset hounds (a much smaller breed), 

 litters of cross-bred pups being produced. 



Iwanoff' has recorded an experiment in which he successfully 

 inseminated a white mouse with the spermatozoa of a white rat. 

 Two hybrid young ones were produced after a pregnancy lasting 

 twenty-seven days. They were intermediate in size between rats 

 and mice. This is the first record of a cross being obtained between 

 two species so different in size as the rat and the mouse, coitus 

 between them being practically impossible. Furthermore, Iwanoff 

 has successfully employed artificial insemination to obtain hybrids 

 between horses and zebras (a cross which is often difficult to get 

 by the normal method owing to the liability of the animals to 

 refuse service). 



The problem of preserving spermatozoa alive in artificial media 

 is one which has onjy recently been investigated systematically. It 

 is evident that were one in a position to send semen to a distance 



1 For further information and practical details see Iwanoff, Die Kunstliohe 

 Befruchtung der Raitstiere, Hannover, 1912. For experiments with fowls see 

 Iwanoff, " Experiences sur la F6condation Artificielles des Oiseaux," C R. de la 

 Soc. M Biol., vol. Ixxv., 1913. 



2 See Huish, loo, dt. 



3 Plonnis, "Kiinstliche Befruchtung einer Hiinden, etc.," Iriaug.-Dissert., 

 Eostock, 1876. 



* AUbrecht, "Kiinstliche Befruchtung," Wochemchr. f. Thierheilkunde wnd 

 Viehzuckt, Jahrg. xxxix. 



^ Heape, " The Artificial Insemination of Mammals," Proc. Roy. Soc, vol. Ixi., 

 1897. 



" Iwanoff, loo. cit. 



21 A 



