PERIPHERAL NERVES, TOPOGRAPHY AND ENDINGS. 315 



motor nerve-endings, and other elements, also stain, though: 

 later than the sensory nerves. He proceeded by injecting frogs 

 through the vena cutanea magnawith 1 c.c.of saturated solution 

 of the colour. The organ to be investigated is removed after 

 the lapse of an hour or two. The stain generally keeps for only 

 a few minutes, unless it is fixed. This may be done by means 

 of iodine. Arnstein proceeds by injecting, a saturated solu- 

 tion of iodine in 1 per cent, solution of iodide of potassium. 

 The organs are then removed and soaked in the iodine solu- 

 tion for from six to twelve hours. They are then washed out 

 with water and put up in acidulated glycerin (see a good 

 abstract of this paper in Zeit. f. wiss. Mik., iv, 1, 1887, p. 84). 

 In a later paper (Anat. Anz., 1887, p. 551 ; see Zeit. f. wiss. 

 Mik., 1887, p. 372) Arnstein gives some further details 

 concerning the reaction, and states that the stain can also be 

 fixed, and even better than by iodine, by means of picro- 

 carmine or picrate of ammonia (see also Journ. Roy. Mic. 

 8oc., 1888, p. 515). 



BIEDERMANN (Sitzb. k. Acad. Wiss. Wien., Math. Nat. CL, 

 1888, p. 8; Zeit. f. wiss. Mik., vi, 1, 1889, p. 65) has been 

 investigating the nerve-endings in the muscles of inver- 

 tebrates by this method. He injects, for instance, 0*5 to 1 c.c. 

 of a nearly saturated solution of methylen blue in 0'6 per cent, 

 salt solution into the thorax of a crayfish, leaves the animal 

 for from two to four hours in a moist chamber, and then kills 

 it. The animal should then be opened, and the muscles 

 exposed in a roomy, moist chamber for from two to four hours 

 before examining them (in all the forms of this method, the 

 presence of oxygen is necessary to the reaction). Instructions 

 as to the minutiae of the process as applied to various objects 

 are given in the papers quoted. 



As far as I can see, this method, which is at present in its 

 infancy, promises to be a very fruitful one. 



655. Peripheral Nerves, Topography and Endings Other 

 Methods. It remains here to be noted that the chief methods 

 for the study of these objects are to be found amongst the 

 gold methods given in Chapters XII, in Part I, and XXVII 

 and XXVIII in Part II. The method of Freud for nerve- 

 centres, which will be given in the next chapter, is also a good 

 one for the study of the topography of peripheral nerves. 



