NORMAL KNEE-JERK. 65
13th to the 14th, however, the barometer began to fall again, and the temperature being nearly sta- tionary, the knee-jerk was again depressed.
These curves show most clearly that the knee-jerk is closely dependent on changes in the weather, but, inasmuch as we are something more than weather- gauges, the variation is qualitative rather than quantitative. The fact that other influences are at work is shown in the course of the curve of the knee-jerk, when looked at as a whole. Thus one observes that the general condition of the subject, when looked at from this standpoint, was falling off during the two weeks, in spite of the fact that the barometer was, on the whole, rising : moreover, this depression of the knee-jerk would seem to be greater than the rise of temperature, which occurred during this time, could account for. The fact is easily explained ; the work involved in the research and in the study of the records gained in the experi- ments was not small, and the fatigue which the sub- ject felt at the end of the fortnight was an un- doubted element in causing the marked falling off of the knee-jerk.
It is no new discovery that the general condition of man is greatly influenced by changes of the weather, but a demonstration of the fact is neverthe- less valuable and may perhaps drive home the lesson already learned by physicians and surgeons in their practice.
It naturally suggests itself that what we call the weather is composed of other conditions beside those recorded by the thermometer and the barometer, and that the direction of the wind, the degree of humidity of the air and the electric potential of the atmosphere
