335 



Nachdruck verboten. 



A Note on Sensory Nerve-endings in the extrinsic Eye-muscles of 

 the Rabbit. "Atypical Motor-endings" of Retzius. 



By G. Carl Huber, 



Assistant Professor of Anatomy and Director of Histological Laboratory, 



University of Michigan. 



With 3 Figures. 



In an account of observations made with the Golgi and methylen 

 blue methods on the motor endings in striated muscle tissue, in a 

 number of invertebrates and numerous vertebrates, Retzius drew at- 

 tention to an atypical motor ending found in the extrinsic eye-muscles 

 of the rabbit. A glance at Plate XVIII of the Biologische Unter- 

 suchungen, Band III, is, as he himself suggests, sufficient evidence 

 that he is not dealing with typical motor endings, such as are found 

 generally in the voluntary muscles of mammals. For a detailed de- 

 scription of these endings, the reader is referred to the communication 

 of Retzius, the following brief extract is here given for the sake of 

 clearness. — After losing their medullary sheath, the nerves, which 

 terminate in the atypical endings, proceed for some distance as non- 

 raedullated fibres. Terminal branches are, however, given off from the 

 medullated portion of these fibres, as they course along between the 

 muscle fibres. These leave the parent fibres at the nodes of Ranvier, 

 either as nonmedullated fibres, or they may be myelated for a segment. 

 The configurations of the endings vary. They may be very simple, 

 consisting of a single unbranched fibre terminating in a single end-disc. 

 Two or three end-discs may be found on one unbranched fibre. Be- 

 tween these simple endings and much more complicated ones, inter- 

 mediary forms are found. Besides the above more localized endings, 

 a number of elongated terminations, consisting of branched or un- 

 branched terminal axis cylinders, beset with variously shaped end- discs, 

 were described. 



In a series of observations, on the nerve endings in striated 

 muscle tissue, made with the methylene blue method, I have had fre- 

 quent opportunity to observe the endings to which reference has here 

 been made, in a large number of preparations of the extrinsic eye- 

 muscles of rabbit stained in methylene blue and mounted in ammonium 



