336 



picrate glycerine, and have been able to confirm the observations made 

 by Retzius in every detail. For some time, however, these endings 

 have been the subject of more careful study, and as a result I have 

 come to look upon them not as "atypical motor endings" but rather 

 as a type of sensory ending. The purpose of this note is to give 

 briefly the observations which led to this conclusion. 



Retzius states that with the atypical endings found in the ex- 

 trinsic eye -muscles of the rabbit such as should be regarded as ty- 

 pical were to be observed. His own words read as follows: "Zwar 

 kommen auch Formen vor, welche als typische aufge- 

 faßt werden können; die meisten aber sind als 'atypi- 

 sche' aufzufassen". This observation I can confirm. The ty- 

 pical motor endings, may be observed in every well stained prepar- 

 ation ; although, as far as my observation goes, they stain less readily 

 than do the atypical forms, of which I will speak in the remaining 

 portion of this article, as sensory eudings. In order to stain the 

 motor endings, I have found it necessary to wait a longer time (one 

 hour to one and one half hours) after the injection of the methylene 

 blue solution, before exposing the muscles, and have further found it 

 necessary to expose the muscle a longer time to the air before the 

 stain is fully developed in the motor endings, than is necessary to 

 obtain well stained preparations of the sensory endings. This may 

 explain why the sensory endings — "atypical motor endings" — were 

 more numerous in the preparations observed by Retzius than were 

 the motor endings — typical forms. Attention may also be drawn to 

 the distribution of these two types of endings. In all the recti muscles 

 of the rabbit — and these were more particularly studied — the motor 

 nerves terminate in the middle third of these muscles. A point which 

 is, however, somewhat difficult to establish, owing to the contraction 

 of these muscles when severed from their attachment. 



The sensory endings are much more numerous in the anterior 

 third of the recti muscles, though they may also be found in the 

 middle third. I have never found the sensory endings in the retractor 

 bulbi, while the motor endings may readily be found in this muscle. 

 On closer inspection the nerve fibres terminating in these two distinct 

 endings, present marked structural differences. The nerve fibres ter- 

 minating in motor endings are in structure like similar nerves in other 

 striated muscle tissue. The medullated motor fibres branch and re- 

 branch before reaching their termination. The branches resulting from 

 a small bundle of nerves usually, however, terminate in a relatively 

 small area. Single motor nerve fibres can not, as a rule, be traced 



