140 Journal of Comparative Neurology, 



a contraction of all of these muscles. This is indeed more or 

 less true in abnormal conditions as I have seen in a patient, 

 who went into a diffuse spasm of all the muscles as soon as he 

 was startled by a touch. In the normal however we find that 

 certain forms of stimuli call forth certain movements. You 

 touch the thumb with a feather, the natural result will be that 

 the thumb moves towards the index finger to press the ob- 

 ject between the two fingers. This means that a certain 

 quality of stimulation throws the sensory neurone into such 

 a state of activity as will appeal to, and arouse, the motor 

 neurones connected with the muscles which bring the thumb 

 and index together. If however a needle or another cutting 

 or pricking object is held against the thumb, the same sen- 

 sory cells are put into a qualitatively different state of activity, 

 to which the motor neurones of the above muscles have un- 

 learned to react, but which arouses the antagonists, those which 

 draw the finger from the object. The fact that so many motor 

 cells are directly or indirectly connected with each sensory 

 neurone, makes such a great variety of movements possible 

 after different kinds of irritation of one and the same sensory 

 neurone. In reality, far more complicated movements are pos- 

 sible. For the great variety of combinations of the muscles of 

 even one segment, the help of the intermediate cells becomes 

 essential ; for a sufficient working together of all the segments 

 in the body this is even more evident. 



In order to give an idea of the complication of all the ne- 

 cessary mechanisms of the whole organism needed for a satis- 

 factory cooperation of all the muscles we pass in a hasty review 

 the principal segments of the vertebrate. They are not all of 

 the same dignity and importance. The segments of the neural 

 tube supplying the tail are necessarily built differently from 

 those supplying the extremities or the trunk or the head. 

 Morphologically there is a striking harmony among the seg- 

 ments behind the skull, as far as the vertebral column extends. 

 The function of these segments is relatively uniform, represent- 

 ing the locomotion, the movements of the trunk, and the 

 extremities. But in the head, greater diversity prevails. As 



