41 
Only during later life, when the position-reflexes develop, the knee 
jerks gradually diminish. Further, a diminution in the position-reflexes 
is accompanied by exaggeration of the patellar tendon reflexes. The 
position-reflexes can be diminished under two circumstances. Firstly, 
the degree of consciousness of the centripetal stimulus can become 
weaker, and, secondly, the centrifugal motor impulse can be disturbed 
in its transmission. In both cases the inhibitory influence on the 
knee jerks will be diminished. The former oceurs during strong 
pre-occupation, so that for instance the knee jerks are exaggerated 
in cases of hysteria, melancholia, or states of anxiety. Moreover, the 
centripetal stimuli will also be perceived less during a general 
relapse of consciousness as occurs normally during deep sleep or 
fatigue. Pathological relapses as Neurasthenia and states of dementia 
are usually accompanied similarly by exaggerated reflexes: The 
motor impulse of the position-reflexes will be disturbed in its trans- 
mission by lesions of the pyramidal systems, through which conse- 
quently the inhibitory influence upon the knee jerk is also absent. 
In accordance with these facts, the knee jerks are diminished 
when strong impressions from without, emotions or other preoccu- 
pations, are as far as possible excluded. Then the adaptation to 
these perpetually centripetal impulses is greatest. 
Other inhibitory influences upon the patellar tendon reflexes are 
also of great importance. SHERRINGTON has shown that each voluntary 
and each reflex muscle-contraction is accompanied by asynchronous 
relaxation of the antagonists. Here too, I should think the question 
must be raised, whether this relaxation of the antagonists is not to 
be regarded as an inhibitory influence from the simultaneous 
contraction of the agonists. A muscle is in a state of a certain 
tension, which is caused by a stimulus originating in the muscle 
itself. This muscle therefore is in a reflex tonus-state, which will 
diminish -— analogous to the inhibition of simultaneous sensations or of 
simultaneous will-impulses, — when synchronous competing afferent 
stimuli arise, as these originating during the stimulus of the knee 
jerks, or when the simultaneous efferent impulses of the knee jerks 
are present. It appears to me, that the simultaneous relaxation of 
the antagonists during contraction of certain muscle-groups, which 
SHERRINGTON drew attention to, should be regarded in this manner. 
It is not even necessary that the agonists contract in order to acquire 
this relaxation of the antagonists. The arm ofa patient with complete 
paralysis of the radial nerve was brought into such a position, that 
the slight tonus of the flexors maintained this position, and that 
without this tonus the arm would be extended by the force of 
