142 ELECTRO-PHYSIOLOGY CHAP. 



blooded animals (dog, rabbit) and in those that are cold-blooded, 

 the number of stimuli acting upon the central organ in a unit of 

 time may be varied within wide limits without interrupting the 



^ 



" 



v^ 



Km. (13. Tetanus curve of Rabbit with direct excitation of spinal cord. The stimulation-frequency 

 varies between 10 ami 34 per sec. (v. Limbeck.) 



uniform rhythmical oscillations (longitudinal or lateral variations) 

 of the excited muscle. This is very evident in the accompanying 

 curve (Fig. 63) obtained by direct stimulation of the spinal 

 cord of rabbit which shows most plainly how the number of 

 muscular contractions per second increases with the number of 

 stimuli sent into the central organ. 



The stimulation -frequency varied in this case between 10 

 and 34, with prolonged tension of the spring of a Neff's hammer 

 in the induction apparatus, the correspondence in number of 

 the single contractions (oscillations) of the muscle being so 

 exact that at the beginning even the make and break effects are 

 visible in the curve, as shown by the greater and lesser indenta- 

 tions. -The same results appeared from other experiments, in 



J 



Fin. r.4. Muscular oscillations in strychnia tetanus (Frog), n, Commencement ; li, end of the 



curve, (v. Limbeck.) 



which a persistent reflex contraction of the muscle was obtained 

 (central excitation of sciatic nerve of opposite side). V. Limbeck 

 failed to discover oscillations in the myogram at stimulation - 

 frequencies employed by Kronecker and Stanley Hall (43 per 

 sec.), as well as Horsley and Schafer ; the curves were almost 



