18 
IOWA ACADEMY OF SCIENCE 
THE THEORY OP BINAURAL BEATS— AN EXPERIMEN- 
TAL CONTRIBUTION. 
G. W. STEWART AND HAROLD STILES. 
(ABSTRACT,) 
The experiments here reported were performed in order to 
secure evidence concerning the cause of the additional maxima 
which occur in binaural beats. (See G. W. Stewart, Physical 
Review, Series 2, 3, p. 146, 1914, for a description of the phe- 
nomena.) These additional maxima occur at certain phase 
differences, and the change in these phase differences should 
depend upon the frequency of the tones, but not upon the fre- 
quency of the beats. If the additional maxima are caused by 
interaural conduction then, as it can be shown, the phase dif- 
ferences should vary as the frequencies. In the accompanying 
curve the phase differences, shown as fractions of YT" , are the 
ordinates and the frequencies, abscissae. Instead of a straight 
line which should obtain in the case of interaural conduction, 
we have a curve which is far from a straight line. (See Plate 
III.) The numbers in parentheses indicate the number of ob- 
servations used in obtaining the position of the point. Five 
frequencies were used. 
After much consideration of theories involving interaural 
conduction, none seems to be in agreement with the evidence 
here shown. 
Physics Laboratories, 
State University op Iowa. 
ON THE LYMPHATIC SYSTEM OF THE COMMON RAT. 
(Epimyus norvegicus) 
THESLE T. JOB. 
(ABSTRACT.) 
From fifty injected specimens, the gross anatomy of the 
Common Rat has been studied and outlined. The results of the 
work have further proven the studies of McClure and Silvester 
on the Lymphatico-venous communications in the Jugulo-sub- 
clavian district, and of Silvester on the renal vein communica- 
