No. 388.] MAINTENANCE OF THE EQUILIBRIUM. 319 
function of this little organ. Even in the lower forms, for 
example in the crabs, Kreidl was able to establish the same 
fact. 
The result of this discovery, as well as the observation of dis- 
eases of the labyrinth in man, has taught us that this part of 
the inner ear, that is, the labyrinth, represents a sense organ 
which gives to the individual information in regard to the posi- 
tion of the head in space. This organ produces the sensation 
of turning, and thus controls the perception and maintenance 
of equilibrium. We have, then, acquired a sense of equilibrium, 
the peripheral sense organ of which is to be found in the laby- 
rinth, and which transmits its sensations to the brain by means 
of a part of the auditory nerve. 
The method of action of this sense organ is as follows: both 
in the utriculus and at places in the semicircular canals, the 
ampullz nerves terminate in cells from which cilia project into 
the inner lumen; there is also in the utriculus, at the end of 
these nerves, a cluster of fine crystals — the otoliths. The utric- 
ulus and semicircular canals are filled with a fluid, the endo- 
lymph, which is agitated by each movement of the head, and 
which thus bends the cilia. The otoliths contribute to the reén- 
forcement of this stimulation. At the beginning of a turn of 
the head in the plane of one of the canals, the fluid, as has been 
shown by Breuer, lags behind, and so strikes in the opposite 
direction against the cilia. 
The task of maintaining the equilibrium is, again, essentially 
lightened by the sense of sight. This point hardly needs a 
detailed presentation. The impressions of vision give us infor- 
mation as to any change in the position of our body, and every 
one knows that we stand or move unsteadily in the dark or with 
closed eyes. And here I will emphasize the fact that the sensa- 
tions from the eye muscles are also essential components of the 
mechanism of equilibration. ; 
Recapitulating, then, we may say that the following sensa- 
tions codperate for the equilibration of our bodies: touch sensa- 
tions, which are perceived by means of nerves from the joints, 
tendons, and muscles; sensations from the labyrinths; and, 
finally, optic sensations. All of these sensations are collected 
