98 TISSUES OF THE NERVOUS SYSTEM. 



stance, which does not project above the surface. The axis- 

 cylinder penetrates into the substance of the prominence, pass- 

 ing through the sarcolemrna, with which its Schwann's sheath 

 becomes continuous. It usually divides dichotomously in the 

 prominence, each branch ending in a rounded extremity. The 

 prominence, therefore, consists of two parts, viz., the axis- 

 cylinder, with its two branches, and the nucleated granular 

 substance in which it is embedded. The granular substance 

 consists, in all probability, of the same material as that which 

 constitutes the so-called muscle-corpuscles. 



Muscular Nerve Endings of the Frog. In many 

 respects the nerves of the muscles of the frog differ from 

 those above described. In the first place, there are many 

 muscular fibres which are entered by only one nerve. In 

 order to make out this fact, it is a good plan to place portions 

 of muscle in a mixture of chlorate of potash and nitric acid 

 at 40 C. ; or, better, to place the tissue for twenty-four hours 

 or more in diluted sulphurous acid, after which it is exposed, 

 still remaining in the liquid, to a temperature of 40 for a few 

 hours. If the muscle is then shaken with water in a test tube, 

 the individual fibres separate very readily from each other, and 

 may be covered without further preparation. For the study of 

 the finer relation of the muscular nerves, separate fasciculi of 

 the gastrocnemius may be employed, which must be cut out 

 with their tendons those parts being chosen to which vessels 

 and nerves can be traced with the naked eye. The preparation 

 is covered in humor aqueus, after it has been spread out with 

 great care with needles. It is then possible to observe that a 

 inedullated fibre comes into contact here and there with a 

 muscular fibre, and divides into several medullated branches. 

 Just as the branches approach the point at which they enter 

 the sarcolemma, in order to attain the surface of the muscular 

 substance, they lose their medullary sheath. At this point, 

 they resolve themselves into a number of small pale filaments, 

 which run parallel to the long axis of the muscle, keeping close 

 to its surface, and are beset with oblong structures resembling 

 nuclei. Eventually, each terminates abruptly in a rounded 

 end. 



Another excellent object for demonstration of the muscular 

 nerves is the thoracic cutaneous muscle of the frog, which 

 must be divided along its insertions, and then severed from its 

 thoracic attachments, and carefully spread out in a drop of 

 humor aqueus and covered, care being taken to interpose strips 

 of paper underneath the edge of the cover-glass. It is also 

 possible to demonstrate the nerve endings iu frog-muscles with 

 the aid of nitrate of silver the same parts being used for the 

 purpose. The isolated fasciculi are placed in serum, to which 

 an equal quantity of distilled water has been added, for ten or 



