Page:The American Journal of Psychology Volume 1.djvu/61

 NORMAL KNEE-JERK.

55

Fig. 11.

April 4th, 1.15 P.M.

when the subject was rapidly multiplying, was 32 mm. (Fig.

no

Reenforcement Caused by Exciting Mental Work. — A good example of the effect of exciting mental work is to be found in the results of the ex- amination at 1.30 P. M., April 5th, when the sub jet repeated to himself Browning's stirring poem — Fig. 12. "How they Brought the Good News Apr!l 5tfl - 1MP ' M ' from Ghent to Aix." The average knee-jerk during the preceding quiet had been 27 mm., and the average taken while the poem was being re- called to memory was 64 mm. (Fig. 12.) In such a case as this, one can- not help thinking that the muscles of the larynx may have been called into play, and that the rhythm of the res- piration may have been altered. The subject was not conscious of making any attempt at phonation, but it did seem to him that his breathing had been longer and deeper.

Effect of Respiration on the Knee-Jerk. — It is interesting to consider, in this connection, the effect of the respiration on the knee-jerk. A few experiments were made with reference to this point, the respiration and the knee-jerk both being recorded on the same moving surface. It was not found in these experiments, however, that the res-