Page:The American Journal of Psychology Volume 1.djvu/47

 NORMAL KNEE-JERK. 41

say that the knee-jerk is generally highest in the early part of the day. This conclusion corresponds with the feeling of the subject, who is usually most vigorous in the early part of the day, but who occa- sionally does not feel like active work until consider- ably later.

The last line of the table contains the averages derived from all the experiments taken at each of the regular examinations, arranged according to the hours at which the examinations were made. These averages corroborate what has been already stated, that there is a diurnal variation of the knee-jerk, that it is greatest in the morning, just after the first meal, and that it is lower at night. This fall- ing off of the knee-jerk can be scarcely attributed to anything except a depression of the condition of the body as a whole dependent on weariness, and, as far as the writer can judge, it is proportional to the degree of fatigue, except when counteracted by some reenforcing influences. Although the knee- jerk tends to become less as the day goes on, one sees in the averages given at the bottom of the table, viz.: 25, 65, 43, 47, 30, 40, 27, that the decline is an interrupted one, and this brings us to the con- sideration of the effect of hunger.

The Effect of Meals on the Knee-Jerk. — It may be stated, as a rule, that the knee-jerk is higher after each meal than before it. This rule, however, like every other, has its exceptions, and they are shown in the following table :

Explanation of the Table. — In this table the aver- age knee-jerk, before and after each meal, is given, and in the columns following the difference between