A HISTORY OF SCIENCE 



principle of irritability and requires the immediate ap- 

 plication of a stimulus to the nervo-muscular fibre 

 itself. These three kinds of muscular motion are well 

 known to physiologists; and I believe they are all 

 which have been hitherto pointed out. There is, 

 however, a fourth, which subsists, in part, after the 

 voluntary and respiratory motions have ceased, by 

 the removal of the cerebrum and medulla oblongata, 

 and which is attached to the medulla spinalis, ceasing 

 itself when this is removed, and leaving the irritability 

 undiminished. In this kind of muscular motion the 

 motive influence does not originate in any central part 

 of the nervous system, but from a distance from that 

 centre; it is neither spontaneous in its action nor di- 

 rect in its course ; it is, on the contrary, excited by the 

 application of appropriate stimuli, which are not, how- 

 ever, applied immediately to the muscular or nervo- 

 muscular fibre, but to certain membraneous parts, 

 whence the impression is carried through the medulla, 

 reflected and reconducted to the part impressed, or 

 conducted to a part remote from it in which muscular 

 contraction is effected. 



11 The first three modes of muscular action are known 

 only by actual movements of muscular contractions. 

 But the reflex function exists as a continuous muscular 

 action, as a power presiding over organs not actually 

 in a state of motion, preserving in some, as the glottis, 

 an open, in others, as the sphincters, a closed form, and 

 in the limbs a due degree of equilibrium or balanced 

 muscular action a function not, I think, hitherto 

 recognized by physiologists. 



" The three kinds of muscular motion hitherto known 



254 



