NORMAL KNEE-JERK. 19
the course of such experiments many of the more ordinary forms of reinforcement would reveal them- selves to us.
Routine of Experiments. — Such a research was ac- cordingly undertaken. The experiments were made on the writer. They extended from April 1st to April 14th inclusive. 1 The condition of the knee- jerk was examined seven times a day, and twenty- five experiments were made at each examination. The hours chosen for the experiments were as fol- lows, viz.: 8.15 A. M., immediately upon rising; 9.15 A. M., soon after breakfast; 1.15 P. M., just before lunch; 2.15 P. M., just after lunch; 6.15 P. M., just before dinner; 8.00 P. M., soon after dinner; and 11 P. M., just before going to bed. For various reasons it was not always possible to make the experiments at exactly the schedule time, but it was seldom that the time of the experiment varied half an hour from that given. The total number of examinations in this series was 93, and the total number of experiments was 2,321. The many experiments which were made at other than the schedule times are not included in these figures.
In the case of each experiment, the hammer was so placed that, when it was hanging free, it just touched the skin over the middle of the ligament. It was then raised through an arc of 40° and allowed to rest on the catch. At the proper moment it was
throughout the period the subject led a regular life, getting up and going to bed at his usual hours, doing his ordinary work and eating his accustomed fare. It is worth noting that no wine or beer was used during the period, but that a cup of coffee was taken with breakfast and dinner, and a cup of tea with lunch. The subject, as was his habit, smoked one or two cigars a day.
