214 
IOWA ACADEMY OF SCIENCE Voi.. XXVIII, 1921 
REFERENCES 
(1) Carlson and Euckhardt: Am. Jour, Physiol., 1920, EIV, 55. 
(2) Arnold: Virchow’s Arch., 1863, XXVIII, 433. 
(3) Smirnow: Anat. Anzeiger, 1888, III, 258. 
(4) Cuccate: Int. Monatschr. f. Anat. u. Physiol., 1888, V, 194. 
(5) Wolff: Arch. f. Anat., 1902, 179. 
(6) Patterson: Am. Jour. Physiol., 1920, EIV, 153. 
De:partment op Physiology 
State University oe Iowa 
