243 



appear when a lens is used which magnifies ten diameters. With a 

 higher power a few fibres or small bundles of fibres may be seen run- 

 ning from the chief nerves of the segment toward the transverse ten- 

 dons which limit the segment. These fine nerve branches are probably 

 sensory. The coarser ones here represented are mainly motor. 



In the regions where the primary segmentation is not well marked 

 the nerve branches give rise to an extensive plexus, as shown in the 

 figure. The rodents which I have examined are mice, rats, rabbits, 

 and guinea-pigs. In mice, the primary segmentation is fairly complete ; 

 in rabbits the areas where it is lacking are proportionally larger than 

 in the guinea-pig, and the peripheral plexus is correspondingly de- 

 veloped. 



The relations of the individual muscle-fibres composing the muscle 

 to the muscle as a whole may be determined either by transferring a 

 muscle prepared as described above into a solution composed of twenty 

 parts of nitric acid, twenty parts of glycerine, and sixty parts of water, 

 or by the following method. The muscle is first impregnated with 

 gold-chloride by one of the usual methods. It is then transferred to 

 pure glycerine and left there for several days. Finally it is placed in 

 the nitric acid and glycerine mixture described above. The nitric acid 

 in both of these methods of preparation serves to destroy the con- 

 nective-tissue of the muscle. The finer medullated fibres fixed in osmic 

 acid are also greatly injured. The muscle-fibres, however, are rendered 

 so tough that they may be readily teased apart without injury. After 

 the gold - chloride treatment very long muscle -fibres may be isolated 

 with the nerve-ending intact, and thus the relation of the nerve-ending 

 to the fibre as a whole may be determined. 



One who has examined fibres prepared by this latter method is 

 not likely to doubt that the sheath of Schwann is intimately united 

 to the sarcolemma and that the nerve -ending lies below the latter. 

 If further proof be desired, small bundles of muscle-fibres may be fixed 

 in osmic acid and digested in pancreatin, as described by Chittenden 1 ). 

 Such fibres often show after the digestion of the protoplasm, an un- 

 digested portion of the nerve-ending adherent to the inner surface of 

 the sarcolemma in the region where the latter fuses with the sheath 

 of Schwann. After impregnation with gold - chloride the protoplasm 

 of the muscle -cell often digests more quickly in pancreatin than do 

 the sarcolemma, the nerve-ending, or the nerve -fibres. In such spe- 



1) Untersuchungen aus dem physiologischen Institut Heidelberg, 

 Bd. 3, 1880, p. 171. 



16* 



