there is any causal relation between the change of external conditions and the observed variation of excitability. It has been shown that the moto-excitability is greatly influenced by temperature. In order to find in what manner the diurnal variation of excitability was influenced by the daily variation of temperature, I took special care to secure by means of the thermograph a continuous record of temperature variations. The table which follows shows the relation between the hours of the day, temperature, and amplitude of response, in a typical case of diurnal variation of excitability.
TABLE II.—SHOWING THE RELATION BETWEEN HOUR OF THE DAY, TEMPERATURE AND EXCITABILITY. (SPRING SPECIMEN.)
| Hours of day. |
Temperature | Amplitude of Response. |
Hours of day. |
Temperature | Amplitude of Response. | |||||||
| 5 | p.m. | 28° | C. | 28 | mm. | 5 | a.m. | 20° | C. | 5 | mm. | |
| 6 | „ | 25.5° | „ | 28 | „ | 6 | „ | 20.5° | „ | 4.2 | „ | |
| 7 | „ | 24.5° | „ | 27 | „ | 7 | „ | 21° | „ | 3.5 | „ | |
| 8 | „ | 23° | „ | 23.5 | „ | 8 | „ | 22° | „ | 2.5 | „ | |
| 9 | „ | 22° | „ | 21.5 | „ | 9 | „ | 24° | „ | 0 | „ | |
| 10 | „ | 21° | „ | 18 | „ | 10 | „ | 26° | „ | 6 | „ | |
| 11 | „ | 20.5° | „ | 15 | „ | 11 | „ | 26.5° | „ | 15.5 | „ | |
| 12 | „ | 20° | „ | 13 | „ | 12 | „ | 28° | „ | 22.5 | „ | |
| 1 | a.m. | 20° | „ | 10 | „ | 1 | p.m. | 28° | „ | 26 | „ | |
| 2 | „ | 20° | „ | 8 | „ | 2 | „ | 28.5° | „ | 28 | „ | |
| 3 | „ | 20° | „ | 7.5 | „ | 3 | „ | 28.5° | „ | 28 | „ | |
| 4 | „ | 19.5° | „ | 6 | „ | 4 | „ | 29° | „ | 28 | „ | |
From the data given in the table, two curves have been obtained. One of these shows the relation between the hours of the day and temperature; the other exhibits the
