337 



for any distance before terminating. Single motor fibres, or small 

 bundles of such, often cross the muscle fibres at right angles. The 

 sensory fibres, on the other hand, may often be traced for long di- 

 stances, either as single fibres or as small bundles before their termin- 

 ation is reached. They have in the main a course parallel to the 

 muscle fibres, between which they run. The sensory fibres branch 

 frequently. This division takes place at the nodes of Ranvier. The 

 resulting branches, of which there may be two, three or even four, 

 diverge more or less, undergo further division, and now and then unite 

 with the branches of other sensory nerves to form a loose plexus. 

 Unless the recti muscles are, after fixing and clearing, forcibly extended, 

 the sensory fibres found in them present a wavy or spiral course. This 

 is brought out in some of the figures given by Retzius. The medul- 

 lary sheath of the sensory fibres undergoes frequent interruptions, 

 bringing the nodes of Ranvier near together. The internodal seg- 

 ments are, therefore, very short, measuring, from 18 f.i to 30 fi in 

 length. The medullated fibres reproduced by Retzius all present these 

 short internodal segments. The single medullated fibres, as also the 

 small bundles of these fibres, are sourrounded by a more or less di- 

 stinct fibrous connective tissue sheath, which I have interpreted as a 

 sheath of Henle, although it is not so prominent as often found in 

 other parts of the body. In this sheath are found numerous con- 

 nective tissue cell nuclei; these with the nuclei of the internodal seg- 

 ments give these fibres in methylene blue preparations, double-stained 

 in alum carmine somewhat the appearance of nonmedullated fibres, 

 suggesting the beaded appearance ascribed to such fibres. These sen- 

 sory fibres, after losing their medullary sheath, can be traced for 

 relatively long distances before terminating. 



In order to be able to study the endings of the sensory fibres 

 more closely, and to determine their relation to the muscle fibres some 

 of the recti muscles of the rabbit were, after staining in methylene 

 blue, fixed in ammonium molybdate (Bethe), embedded in paraffin and 

 cut in longitudinal and transverse sections; these, after fixation to 

 cover glasses, were further stained in alum carmine. 



Huber and De Witt x ) have, in a recent article, published the 

 results of an investigation on the innervation of motor tissue in which 

 investigation the above method was used. Among other endings de- 



1) Huber and De Witt, A Contribution on the Motor Nerve-endings 

 and on the Nerve - endings in the Muscle - spindles. Journ. of Comp. 

 Neurol., Vol. 7, Nos. 3 and 4, March, 1898. 



