GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. Ill 



oblique or arrow markings (incisures of Schmidt) (Fig. 43, /), 

 which seem first to have been accurately described by Schmidt, 

 of New Orleans, later by Lantermann, of Cleveland, Shaw, and 

 others. The same appearances can be also obtained by the use 

 of iodized serum. 



The double contour is not visible in all the myelinic nerves, 

 but is most marked where they show varicose swellings, a con- 

 dition that is due to a preponder- 

 ance of myeline at the enlarged 

 point. From this fact and anoth- 

 er, that the drops of myeline when 

 separated from the fibre show the 

 same double contour, it is argued 

 that the double marking in the 

 fibre is due to a refracting (double) 

 of the myeline, and has nothing to 

 do with the membranous sheath. 

 These varicosities just mentioned 

 are not to be confounded with the 

 bulgings of the ultimate fibrils, or 

 with the " necklace " appearances 

 seen in the course of the fibres of 

 Remak, both of which latter may 

 probably be regarded as artificial 

 productions, either from stretching 

 in the act of teasing or from the 

 imbibition of water. In the brain 

 of the calf they are frequently seen, 

 and they are said to be found in the 

 intracranial part of the olfactory, 

 optic, and acoustic nerves. The 

 fibres in which this change occurs 

 are usually quite small. 



Staining in picro-carmine. 



This reagent has been recommended by Ranvier. It is satis- 

 factorily prepared by Rutherford's process. 1 Taking precau- 

 tions not to injure the nerve in removing it, mount in the solu- 



1 He takes 100 c.c. of a saturated solution of picric acid. Next he prepares an 

 ammoniacal solution of carmine by dissolving one gramme in a few c, c. of water, 

 with the aid of an excess of ammonia and heat. He then boils the picric acid solu- 

 tion on a sand-bath, and when boiling adds the carmine solution. The mixture is 



Fio. 43. a, Myelinic fibre in a state of 

 " coagulation ; " &, myeline exuding from 

 the broken end of the fibre ; c, drops of mye- 

 line separated from the nerve-fibre ; rf, axis 

 cylinder ; <?, nucleus of Henle's sheath ; /, 

 arrow markings. 



