ON THE DEVELOPMENT OF THE NEURO-MUSCULAR 



SPINDLE IN THE EXTRINSIC EYE MUSCLES 



OF THE PIG 



ALAN CALLENDER SUTTON 



From the Anatomical Laboratory, John Hopkins University 



TWELVE FIGURES 



Since Hassal in 1851 first pointed out the presence of spindle- 

 shaped nerve endings in muscle, nearly all anatomists and neurolo- 

 gists have at one time or another in their work become deeply 

 interested in them. The problems which they offer seem to fall 

 naturally into the three great groups — separate yet intimately 

 associated — which divide the research that has been done upon 

 most of the integral parts of the body, namely, the structural or 

 histological studies; the functional side, including both physiologi- 

 cal and pathological aspects; and finally, the embryological de- 

 velopment. The sensory nerve endings in muscle were first ap- 

 proached from the histological side, obviously because methods 

 for such investigation were at hand, and an adequate histological 

 picture of the adult structure is the only sound basis for further 

 advance. This was furnished first by Kolliker in 1862 and dur- 

 ing the next year by Kiihne, to whom we owe the term ' muscle 

 spindle.' Since then, with the development of better w^a3\s for 

 demonstrating the finer structure of the nervous system, such as 

 the vital methylene blue method and the use of silver nitrate as 

 a neuro-fibril stain, additional points have been added by vari- 

 ous workers, among whom are Golgi, Dogiel, Sihler and Huber. 

 They seem to have left little to be desired as to the structure of 

 the ending. I can think of one question, however, that others 

 have asked which has never been answered. Do the sensory 

 endings in muscle have an intermediate substance comparable 

 to that in the motor endings — the receptive 'substance' of 



117 



