15.2 spaces between stimulus and initiation of response. The latent period of the specimen is therefore .076 of a second.
I have been able, moreover, to construct a vibrating-recorder whose frequency is 500 times per second, a fact which enables an easy determination of time-intervals of less than a thousandth of a second to be made. These recorders, owing to their excessive lightness, possess the additional advantage of having a very small moment of inertia. It is obvious, therefore, that the employment of such recorders not only bears favourable comparison with those at present used in animal physiology, but would also
Fig. 70.—The previous record magnified.
have the advantage of reducing the error due to inertia to the lowest possible minimum, and of making the record itself its own chronogram.
It has been said that owing to the extreme lightness of the vibrating-recorder, the slight error usually due to instrumental inertia is here negligible. To what extent this is true may be judged by taking records from the same leaf with two separate recorders of different sizes and comparing the results. If the factors of inertia were prominent, then two such determinations of an identical latent period would give results varying somewhat from each other. I therefore took two different records from the
