LACTASE IN INTESTINE. 31 



intestines of animals can be made to adapt themselves to any particular 

 diet. 



In addition to these results I have been able to determine at what 

 period in the life-history of the rat lactase first appears. Embryos 

 about 2 days before birth had no lactase in their alimentary canal, 

 whereas about 12 hours before birth lactase had appeared. 



The guinea-pig, as the figures show, already loses its lactase in 

 5 weeks after birth, and it would be interesting to know whether by 

 continuous milk-feeding from birth, the enzyme could be kept from 

 disappearing. Experiments in this direction are being carried out and 

 some also in order to determine how soon before birth the enzyme 

 appears. 



Throughout these experiments I have been greatly helped by Miss 

 Lane-Claypon, to whom I owe my thanks. 



In conclusion, I wish to acknowledge my indebtedness to the Government Grant 

 Committee of the Royal Society for a grant which has defrayed the expenses of this 

 research. 



REFERENCES. 



(1) B. H. A. Plimmer. This Journal, xxxiv. p. 93. 1906. 



(2) E. Fischer and W. Niebel. Sitzber. Akad. Wiss. Berlin, p. 73. 1896. - 



(3) E. Weinland. Zeit. f. Biologic, xxxvm. p. 16. 1899. 



(4) Portier etBierry. Compt. rend. Soc. Biol. LII. p. 423. 1900 ; Lin. p. 810. 1901. 



(5) A. Eichaud. Comp. rend. Soc. Biol. LII. p. 416. 1900. 



(6) C. Hugh Neilson and 0. P. Terry. Amer. Journ. Physiol. xv. p. 406. 1906. 



(7) A. Dastre. Archives de Physiol. p. 718. 1889; p. 103. 1899. 



(8) F. Bohmann und J. Lappe. Ber. deut. Chem. Ges. xxvni. p. 2506. 1895. 



(9) P. Portier. Compt. rend. Soc. Biol., v. p. 387. 1898. 



(10) W. Pantz und J. Vogl. Zeit. f. Biol. xxxn. p. 303. 1895. 



(11) L. Langstein und F. Steinitz. Beitr. chem. Physiol. u. Path. vn. p. 575. 1906 



(12) Ch. Porcher. Compt. rend. Soc. Biol. LX. p. 1114. 1906. 



(13) H. Bierry et Gmo-Salazar. Comp. rend. Soc. Biol. LVI. p. 181. 1904. 



(14) L. B. Mendel. Amer. Journ. Physiol. xv. Proc. xni. 1905. 



(15) Ch. Porcher. Compt. rend. CXL. p. 1406. 1905. 



(16) E. Pfluger. Pfluger's Archiv. xcvi. p. 105. 1903. 



