220 



PRACTICAL HISTOLOGY. 



[XVIII. 



12. Nerves of Frog's Sartorius. Suppose the sartorius to be selected. A 

 beautiful view of the distribution of the motor nerves black is obtained 

 (fig. 203). 



The single nerve-trunk enters the muscle on the median 

 aspect and on its imder surface about the level between 

 the middle and lowest thirds, Several large brandies 

 usually two run nearly parallel towards both ends of the 

 muscle two longer, towards the upper end of the muscle 

 A and two or three shorter, towards its lower end, the 

 latter following a slightly more oblique course. Numerous 

 branches form elongated quadrilateral meshes. At two 

 points in the muscle, towards its ends, there are more fine 

 branches than elsewhere. The fibres form plexuses and 

 divide. Note specially that the knee and pelvic ends are 

 devoid of nerve-fibres. 



13. Motor Nerve-Endings. (i.) Take a thin muscle, 

 e.g., the eye-muscles or intercostal muscles of a small 

 mammal, the thin leg muscles of a lizard, or the thin 

 cutaneous muscles which pass between the skin and the 

 wall of the chest in snakes, and stain them with gold 

 chloride by the formic acid gold chloride method (p. 79). 

 They must remain in the gold solution about one hour. 

 The gold may be reduced, either in water acidulated with 

 acetic acid, by exposure to the light, or in the dark, in 

 25 per cent, formic acid. 



(H) Tease a piece of the purplish- violet muscle in 

 glycerine, and search for a purple nerve-fibre termination 

 in an arborescent branched end-plate lying on the sarcous 

 substance of the muscle (fig. 204). Nuclei are present in 

 the protoplasm of the end-plate. 



(ii.) Golgi's Method. Place the muscles of a newly- 

 killed lizard for a minute or two in a .5 per cent, solution 

 of arsenic acid, and directly afterwards in a solution of 

 .5 per cent, solution of chloride of gold and potassium for 

 1 5-20 minutes, and reduce the tissue in sunlight in a I per 

 cent, solution of arsenic acid. Instead of the above gold 

 solution, use the following mixture, devised by Kiihne : 



Arsenic acid (.5 per cent.) . . . . 60 cc. 



Osmic acid (2 per cent.) . . . 3 ,, 



Chloride of gold and potassium (i per cent.). 12 ,, 



The tissue is then placed in I per cent, arsenic acid, and reduced by exposure 

 to sunlight. The process may be greatly hastened by doing the reduction 

 process at a temperature of 50 C., but it must be done in the direct rays of the 

 sun. The pieces of tissue can be preserved in the following fluid, devised by 

 Mays : 



Glycerine . . . . . . . 60 cc. 



Arsenic acid ( I per cent.) . . . .10,, 



Methylic alcohol . . . . .10,, 



Water . . . . . . . 20 ,, 



In working with solutions of gold, do not use steel instruments. They must 

 be either glass, platinum-iridiurn, or the substance known as " nickeline." 



In birds, reptiles, and mammals the nerve-fibres terminate in " end-plates," 

 which are disc-shaped bodies lying under the sarcolernma, i.e., they are hypo- 

 lemmal in position, 40-60 /u, long and 40 ^ broad. They consist of a finely 

 granular protoplasm with nuclei. As the gold chloride stains only the axis- 



FlG. 203. Distribu- 

 tion of Nerve- 

 Fibres in the 

 Frog's Sartorius. 

 A. Upper, B. 

 Lower end ; aa 

 and bb. Numer- 

 ous fine branches ; 

 P. Pelvic end, and 

 A'. Knee end, with 

 no nerve-fibres. 



