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Mr. W. A. Jolly. Rejiex Times in the 



procedure at the time of experiment was rendered unnecessary by employing 

 the mechanical stimulus of a tap by a slight hammer to the toes, or a squeeze 

 of the toes, and the electrical changes in the limb muscles were recorded by 

 means of the wicks of non-polarisable electrodes, moistened with salt solution 

 and impregnated with kaolin, bound round the limb over the unbroken skin. 

 The wicks were applied at knee and ankle, or thigh and ankle, the skin area 

 covered by each wick being about 1'5 cm. broad. The advantage of this 

 method of leading off is that there is no injury done to the preparation, 

 which can be experimented with for months. A disadvantage is that one 

 cannot record in this way the pure response of a single muscle nor control 

 exactly the points led off from, and the form of the electrical response is 

 found accordingly to be rather variable. The application of a mechanical 

 stimulus to the toes instead of electrical stimulation of a nerve, besides being 

 more " natural," is advantageous from its avoiding injury to the preparation, 

 and also by avoiding the difficulties which arise in recording and interpreting 

 the electrical response when the stimulus is also electrical. Precautions will 

 prevent an induction shock given to a dissected-out nerve from affecting the 

 galvanometer, but it is often difficult to get rid of some slight action upon 

 the string, and the absence of this complication makes me more confident in 

 interpreting the curves. There is also no danger of the stimulus spreading 

 further than is desired. The disadvantage of the use of a tap or squeeze is 

 that a direct stimulation of muscle or nerve might perhaps be caused, whose 

 electrical expression would be visible on the record and be mistaken for a 

 reflex effect. This is a real difficulty in the case of homonymous stimulation, 

 and the attempt has been made to avoid it by stimulating the toes alone and 

 not the rest of the foot. The difficulty does not arise in the case of the 

 heteronymous reflex where the electrodes are applied to the limb opposite to 

 the one stimulated. Here there is no appearance on the records of anything 

 which could be the expression of a direct excitation of the foot. 



The photographic records of the galvanometer movements are made upon 

 plates falling behind the slit of Cremer's apparatus at a rate of about 1 metre 

 per second. The shadow of the string of a small string galvanometer with 

 electromagnet is also thrown on the slit and signals the moment of stimula- 

 tion. A tuning-fork, vibrating at the rate of 200 D.V. per second in front of 

 the slit, throws its shadow on the plate and serves as time marker. The 

 vertical lines showing the direction of the slit are produced by the teeth of an 

 episkotister. In some cases the episkotister has not been used. The curves 

 are measured by the aid of an enlarging camera. The intervals of time are 

 given in thousandths of a second (o-), fractions are also given. 



The frog is suspended in a jacket with the head bandaged as a precaution 



