480 Analysis of Voluntary Muscular Movements. [Mar. 21, 



educated and uneducated classes is not so marked as in the case of 



writing. 



"With regard to finger- movements it was found that they retained 

 nearly the same velocity for all classes between the ages of 20 and 

 50 ; and that in the one case of a man over that age (a labourer, 

 set. 62) there was a decided decrease. 



In the two pathological cases investigated, one of lateral sclerosis 

 in a man of 41, and one of tremor of the hands, following upon 

 syphilis, in a man of 50, similar results were obtained. For the 

 complex movements of writing were most seriously retarded, the 

 pen-movements less, and the finger-movements least of all. 



It appears, then, that as a movement increases in complexity, and 

 involves in its performance the associated action of a greater number 

 of muscles, its velocity diminishes, and the influence of education 

 becomes more distinctly manifest. And as complex movements 

 require a longer education for their rapid performance, so they appear 

 to become sooner defective than the simpler movements. For it is in 

 writing that the retarding effect of age is most apparent, while it is 

 least so in the finger-movement. 



In the second part of the investigation it was desired to obtain 

 tracings from a larger series of contractions than could be registered 

 upon a microscopic slide. For this purpose new instruments were 

 required, and owing to the long delay in making these, but few 

 experiments have been recorded. The instrument finally adopted 

 consisted in a long steel bar, held firmly in an iron clip, and carrying 

 in a clamp attached to one end a smoked glass plate 6 inches square. 

 It was set in motion by an electro-magnet through which passed the 

 current from a storage battery, and, as determined by the chrono- 

 graph, it made fifty-four double vibrations per second. At Professor 

 McKendrick's suggestion it was determined rather to investigate 

 with this instrument the phenomena of fatigue, a purpose for which 

 he thought it very suitable. With this object, Mosso's ergograph 

 was adapted to the instrument, the recording part of which could be 

 pulled on rails slowly away from under the registering lever, which 

 worked up and down with the movement of the weighted finger. 

 Thus a series of contractions and relaxations, divided by the oscilla- 

 tions of the bar into fifty-fourths of a second, was registered on each 

 plate. The plate could be taken out, and a new one substituted, 

 beneath the lever, without stopping the movement of the finger. A 

 key was interposed in the circuit to shut off the current while the 

 plates were being changed. 



Four normal and two pathological cases were investigated, series 

 of tracings being taken with a f kilo., a 1 kilo., and a 2 kilo, weight. 

 They show in a very striking manner the diminution in height of 

 the contraction, and the coincident diminution in its velocity, due to 



