( 709 ) 
Those which have been made in the last six years, are, it is true, 
not so numerous and extensive as I should wish, but an enumeration 
with a list , of the publications may follow here in order to serve as 
an example of what is to be reached in a sound-free apartment. 
1. The sensation of stillness may be experimented on; unless a 
perforation of the tympanum exists, a kind of buzzing may be 
observed, in which at a closer analysis a soft rustling as of the wind 
in the tops of the trees, accompanied by a high-toned whistling (±< 7 *) 
may be distinguished; persons in whom this physiological ear-buzzing 
is indistinct, perceive a feeling of oppression *). 
2. The influence of the adaptation may be traced; then appears 
among others a gradual diminution of the physiological tinnitus 
aurium, which after a 3 hours’ stay in the sound-free apartment has 
entirely disappeared (Bobtolotti), whilst at the same time the feeling 
of oppression, if existing, gradually increases (Minkema) ; from this 
one might be inclined to derive that the physiological ear-buzzing, 
entirely or partly, possesses the character of an after-image *). 
3. The phenomenon of accommodation, discovered by Hensen, 
may be more closely studied, by conveying to a person standing 
outside the camera silenta through bone-conduction the tone of a 
tuning-fork, which then from the person’s ear is conducted into the 
apartment through an auditory tube; whenever a metronome placed 
outside the apartment is ticking, the sample-person accommodates and 
the observer bears a strengthened sound (Qdtx). 
4. From the shortest exposition-time the smallest observable 
number of sound-vibrations may be derived in the tone of a tuning- 
fork or that of an organ, conducted to it from the outside; according 
to Bode this number seems to vary in the scale in a typical manner 
(dk Groot s ) and van Mens). 
i) For my ear the physiological ear-buzzing can be suppressed: a. by the ticking 
of a watch; b. by the sound of a tuning-fork of the c'-pitch and a sound-force of 
68.10-3 Erg. per cm. 2 and per sec. (Erg. d. Physiol. 1905 p. 452). 
3 ) According to Bortolotti the buzzing returns directly, after one has left the 
camera for a moment and then returns. 
s) h. de Groot, Ztschr. f. Sinnesphysiol. Bd. 44 p. 18 and Onderz. Physiol, Lab, 
(5) X p. 137, 
