Pars Anterior and Reproductive Glands. 27 



litter were taken, one pair being given small quantities of extract 

 of pars anterior, the other pair used as a control. The animals 

 fed with the extract bred sooner and oftener than the controls. 

 Posterior lobe extract of pituitary gland had no such effect. 

 Conclusions. — The following conclusions seem warranted : 



I. Pituitary extract, and particularly extract of pars anterior, 

 has a markedly stimulating effect upon the growth and develop- 

 ment of the reproductive glands in young rats of both sexes, as 

 evidenced by histological examination. 



I I . Extract of pars anterior tends to cause early and frequent 

 breeding. Posterior lobe extract has no such effect. 



III. Posterior lobe and ovarian (corpus luteum) extracts 

 apparently do not stimulate sexual development. 



16 (833) 



On the correlation between the number of mammae of the dam 

 and size of litter in mammals. I. Interracial correlation. 



By Raymond Pearl. 



[From the Biological Laboratory of the Maine Agricultural 

 Experiment Station.] 1 



In his breeding experiments with sheep at Beinn Breagh, 

 Alexander Graham Bell 2 found that as the number of nipples of 

 the ewes increased there was a tendency towards a more frequent 

 production of twins and triplets. Regarding this point he says 

 (loc. cit., p. 383): "The indications are that our six-nippled stock 

 will ultimately turn out to be twin bearers, as a rule, when they 

 become fully mature." 



In reporting a case of unusually high, and probably inherited, 

 fertility in the cow I have 3 noted that the individual exhibiting 

 this high fertility bore two supernumerary mammae. 



There is an obvious teleological aspect to this matter. In a 

 general way it is clear that as the number of young born in a litter 

 increases there must be a compensating increase in the number of 



1 Paper No. 52. 



2 Science, N. S., Vol. 36, pp. 378-384, 1912. 



3 Me. Agr. Exp. Sta. Ann. Rept. for 1912, pp. 250-282. 



