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70. GRAVITY CHRONOMETER. Used for measuring, by means of 
a falling screen, very small times of exposure of an object to 
the eye. 
71. TACHISTOSCOPE. Designed by Dr. Harold Griffing, Columbia 
College. Constructed on the principle of the above-mentioned 
chronometer. The object of this instrument is to expose 
letters for a tenth of asecond. Is being used in a special in- 
vestigation of the accuracy of perception at different ages. 
72. HARMONIUM. In which the intervals are not equal, but in 
which they stand in the relation to each other required by 
theory. 
73. KYMOGRAPH. With electric motor attachment, of a very high 
rate of speed, with fixed drum and movable carriage. 
DEPARTMENT OF PHYSIOLOGY. 
In charge of Dr. John G. Curtis. 
74. MODELS of the brain and other organs illustrating the use of 
- inexpensive materials for purposes of physiological teaching. 
Exhibited by Prof. W. Gilman Thompson, M.D., of the Medi- 
cal Department of the University of the City of New York. 
75. KUHNE’S SCHEMATIC EYE and accessories. 
76. VON HELMHOLTZ’S working model of the ossicles of the 
human ear. 
77. APPARATUS to illustrate a well-known optical delusion. 
78. APPARATUS for the study of the contraction of muscle, as 
follows: 
Ludwig’s drum myograph. 
Basel stand. 
Moist chamber and muscle-forceps. 
Tigerstedt’s muscle-lever. 
du Bois Reymond’s induction coil. 
du Bois Reymond’s friction-key. 
du Bois Reymond’s mercurial key. 
Pfeil’s chronograph (2 specimens). 
