54
LOMBARD :
Fig. lO.
April 2nd, 8.15 P.M.
ten experiments was 19 mm. The next two blows were struck just after the subject had been spoken to, and the knee-jerks were 48 mm. and 40 mm. (See Fig. 10; see, also, Fig 9 and Fig. 6.)
Effect of Different Forms of Cerebral Activity. — The experi- ments which we made with refer- ence to the effect of different forms of cerebral activity were far too few to offer a basis for positive conclusions, but it seemed to us that it was the emotional forms of activity which had the greatest influence on the process. Thus, in the case of mental arithmetic, the simple act of multiplying two numbers, even if they were difficult, did not seem to affect the knee-jerk especially, unless the endeavor was made to obtain the result as quickly as possible and the subject were excited by the attempt. The question is worthy of an especial research. One great difficulty in such a research arises from the fact that the experimentor cannot time the blow so as to get the knee-jerk at the moment when the mind of the subject is most actively employed. It is possible that such experi- ments might be combined with plethysmographic ex- periments to advantage.
Effect of Multiplication. — At the examination at 1.15 P. M., April 4th, we tried the effect of multiplication. The average knee-jerk at the time was 20 mm., while the average during the period
