EXPERIMENTAL PSYCHOLOGY 



may be distinguished in another way. The muscles 

 of voluntary motion and of respiration may be excited 

 by stimulating the nerves which supply them, in any 

 part of their course, whether at their source as a part 

 of the medulla oblongata or the medulla spinalis or ex- 

 terior to the spinal canal: the muscles of involuntary 

 motion are chiefly excited by the actual contact of 

 stimuli. In the case of the reflex function alone the 

 muscles are excited by a stimulus acting mediately 

 and indirectly in a curved and reflex course, along 

 superficial subcutaneous or submucous nerves proceed- 

 ing from the medulla. The first three of these causes 

 of muscular motion may act on detached limbs or 

 muscles. The last requires the connection with the 

 medulla to be preserved entire. 



"All the kinds of muscular motion may be unduly 

 excited, but the reflex function is peculiar in being 

 excitable in two modes of action, not previously sub- 

 sisting in the animal economy, as in the case of sneezing, 

 coughing, vomiting, etc. The reflex function also 

 admits of being permanently diminished or augmented 

 and of taking on some other morbid forms of which I 

 shall treat hereafter. 



" Before I proceed to the details of the experiments 

 upon which this disposition rests, it may be well to 

 point out several instances in illustration of the various 

 sources of and the modes of muscular action which 

 have been enumerated. None can be more familiar 

 than the act of swallowing. Yet how complicated is 

 the act! The apprehension of the food by the teeth 

 and tongue, etc., is voluntary, and cannot, therefore, 

 take place in an animal from which the cerebrum is 



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