v SPINAL COED AND NERVES 327 



The true reflex character of the patellar reflex or tendon 

 phenomenon is not universally admitted. According to Brissaud, 

 Eulenberg, Mac William, Waller, Gowers, and others, the time 

 elapsing between the mechanical stimulation and the muscular 

 reaction is too brief for a reflex (via afferent root, cord, and motor 

 root cells), and corresponds approximately to the latent period in 

 direct electrical excitation of the muscle, as shown by the curve of 

 Fig. 189. 



But its reflex nature was clearly brought out by Sciamanna 

 (1900) in some ingenious experiments on a patient with marked 

 exaggerations of the knee-jerk on the right side ; the right vastus 

 internus muscle also contracted reflexly when the patellar tendon 

 on the left side was tapped. By means of the graphic method he 

 showed that the direct and reflex contractions of the leg excited and 



FIG. 189. Comparison of latent period in (1) a direct contraction, (2) the tendon phenomenon, 

 (3) a reflex contraction. On the rabbit. (Waller.) 



those of the opposite side differ perceptibly in the time lost from 

 the moment of stimulation. 



Scheven's latest experiments in Langendorffs laboratory are 

 also decidedly in favour of the reflex nature of the knee-jerk. In 

 the rabbit he compared the latent period in direct electrical 

 stimulation of the muscle and after mechanical stimulation of the 

 patellar tendon. His method enabled him to record the moment 

 of stimulation with great accuracy in both cases, while he avoided 

 the usual errors due to inertia of the lever. On direct stimulation 

 of the muscle he found the latent period to be on an average 

 O'Oll sec., while in the knee-jerk it amounted to 0'022 sec., i.e. 

 nearly double the former. This is excellently shown in Fig. 190, 

 in which the upper line (c?.s.) gives the curve of the m. extensor 

 cruris with direct stimulation ; the lower (r.s.), which starts much 

 later from the abscissa, shows the mechanically excited reflex 

 contraction of the same muscle. 



Scheven also recorded a long series of patellar reflexes evoked 

 by rhythmical stimuli, with the object of establishing the 

 influence of specific conditions of stimulation 011 the height 



