174 SCIENCE PROGEESS 
OuRWALL, Shand. Arch. f. Physiol. 7, p. 222 (1897). 
PFLUGER, Pfiiigers Arch. 6, p. 43 (1871); 10, p. 251 (1875) ; 14, p. 5 (1878). 
Spiro, Zeit. f. physiol. Chem. 1, p. 111 (1878). 
THUNBERG, Shand. Arch. f. Physiol. 17, p. 133 (1905). 
VERWORN, Arch. f. (Anat. u.) Physiol. (1900), Suppl. p. 152; also “Die Biogen- 
hypothese” (Jena, 1903). 
VERNON, Journ. Physiol. 35, p. 53 (1906); Zezt. f. allgem. Physiol. 6, p. 393 
(1907). 
WINTERSTEIN, Zezt. f. allgem. Physiol. 6, p. 315 (1907). 
