58 LOMBAED :
from painful sensory impressions, from voluntary- actions, from emotional activity, or from functional disturbance of the spinal centers, is hard to say, since all these causes seemed to take part in pro- ducing the result.
Reenforcement of the Knee-Jerk Caused by Music, — Perhaps the most interesting of all the forms of reenforcement attributable to cerebral ac- tion, which we saw, was that produced by music. Not all forms of music have this power, however, and, as far as we have been able to judge, it is confined to such as are capable of exciting an emo- tional interest. For instance, the writer can state that "Beautiful Spring," when played by a hand- organ, has little or no effect upon his knee-jerk, although a good military band, when playing a stirring march, is able to cause a very decided reenforcement.
One day during the experiments a procession passed the end of the street, a short distance away, and the effect of the music was very evident. The twenty-five experiments of the examination which had just been made had shown the average knee-jerk to be 32 mm. At the approach of the procession the subject resumed his place on the apparatus, but the first blow was not struck until the first band was passing the end of the street — 60, 71, 74, 70, 60, 55 — another band immediately followed, and it began to play "My Maryland" just before it reached the street— 62, 76, 76, 74, 71, 66, 59, 64, 59— this was followed by a drum corps — 48, 55, 51, 55, 53, 49, 52 — and then the music died away in the distance and only the ordinary street sounds remained — 40, 45, 37,
