ii SENSIBILITY OF THE INTERNAL OKGANS 97 



in change of form of the spindles. In a word, they function as 

 isotonic dynamometers, by which the centres become aware of the 

 degree of active contraction of the muscle and perhaps also of the 

 degree of passive traction to which it is subjected by the action of 

 the antagonist muscles. This hypothesis seems to us simpler and 

 more acceptable than that of other authors who maintain that the 

 sensitive ends of the spindles are excited by the action-current 

 developed in the muscle, or by the molecular chemical changes 

 that take place in it during the contraction. 



While the sensory nerve-endings in the spindles are in direct 

 relation with the muscle fibres, and the stimulus to which they 

 react is given by the form changes of the muscle, the sensory 

 endings in the organs of Golgi are in relation with the tendinous 

 ^fibres, and the mechanical stimulus to which they react is produced 

 by the tension they are subjected to in consequence of the active 

 state of the muscle. While the former function as isotonic 

 dynamometers, the latter function as isometric dynamometers that 

 is, they signal to the centres the tension changes, rather than the 

 form changes of the muscle. For the due performance of this 

 function it is unnecessary to predicate any extensibility of the 

 tendinous organs of Golgi, as was assumed by Cipollone. In fact, 

 if they were extensible their isometric signals would be incorrect. 



According to Marchi, the muscles of the eye-ball contain no 

 other sensory organs capable of signalling the delicate antagonism 

 of their functions, which proves that the musculo-tendinous organs 

 must be able to send intelligence of the least traction exerted by 

 these muscles. 



To explain this great sensibility of the organs of Golgi, 

 Cipollone happily takes into consideration their curved form 

 and oblique position in respect of the tendinous fascia, and the 

 occasionally undulating course of the tendinous fibrils of which 

 they consist. It is evident that, under these conditions, the 

 tendinous organs of Golgi can be affected even by the weak 

 traction exerted on them by the muscle ; there is no real increase 

 in their length, but an adjustment of the fibres that run curved, 

 undulating or obliquely to the line of traction of the muscle. 

 This adjustment or displacement may be accepted as a stimulus 

 adequate to excite the nerve-endings mechanically. 



As regards the functional value of the modified Pacinian 

 organs present in the motor system, particularly in the tendons, 

 bones, and articular tissues in general, Sherrington correctly points, 

 out that they are by their position, and particularly from their 

 structure, eminently suited to signal the different degrees of 

 compression that occur during the changes of relation of the 

 articular surfaces, whether these are actively produced or passively 

 imposed. 



Which of these three different sensory organs located in the 



VOL. IV H 



