170 Prof. A. B. Macallum and Miss M. L. Menten. [July 24, 



As obviously there could not have been any transversely disposed lamina- 

 tion of the albumen in the capillary tube, the result found by Boehm could 

 only be due to physico-chemical causes, and Boveri employs it to explain the 

 production of Frommann's lines. In the lymphatic fluid surrounding the 

 nerve fibrillae sodium chloride is dissolved, and this gives with the silver 

 solution a precipitate of silver chloride, which in light is reduced and appears 

 as black granules. The medullary sheath acts the part of the wall of the 

 glass capillary tube and prevents the entrance of the reagent except at the 

 nodes or at the torn ends of the fibre, but at these points it slowly diffuses 

 into the axial space. Boveri is inclined to explain the result as due to the 

 penetrating solution losing, through the formation of the precipitate, its 

 silver salt, so that for a time pure water only continues to penetrate until the 

 loss is replaced by silver nitrate diffusing forward, whereupon a new 

 precipitate occurs, but at an advanced point, and water alone again continues 

 to diffuse with the same repetition of result. In this also Boveri finds an 

 explanation for the greater distance separating the lines the more remote 

 they are from the point of entrance, as with the distance from that point a 

 greater interval of the capillary tubule must be traversed before the silver 

 salt can be replaced. 



Boveri found further, in small fibres of the sympathetic, a silver precipitate 

 arranged as two parallel bands in the medulla, one on each side of and 

 immediately adjacent to the node of Banvier. Another precipitate he 

 observed not infrequently in the segments or imbrications of Lanterman. 



Joseph,* by treating fresh nerve fibres with a 05 per cent, solution of 

 nitrate of silver containing also 5 per cent, free nitric acid, for several hours, 

 and then with solutions of potassium bichromate, found Frommann's lines 

 equally well marked far from the nodes of Ranvier, as at the latter points and 

 over long extents of the fibres. The striae were formed of granules. 



According to Jakimovitch,f who used special methods of applying the 

 nitrate of silver, the striation of the axon is of three kinds, the difference 

 depending on the breadth of the striae, on the distance between the neighbour- 

 ing bands, and on the character of the granules composing the striae. The 

 lines were present in the fibres of a puppy two days old but not in its optic or 

 abductor nerves, though they were found in such in older puppies with the 

 eyes opened. In winter frogs kept in the laboratory the axons were nearly 

 always diffusely granular, not striated, or if striation obtained it was of a feebly 



* " Uber einige Bestandtheile der peripheren markhaltigen Nervenfaser," ' Sitzungs- 

 ber. k. Preuss. Akad. zu Berlin,' 1888, p. 1321. . 



t " Sur la Structure du Cylindre-axe et des Cellules Nerveuses," ' Journ. de l'Anat. et 

 de la Physiol.,' 1888, p. L42. 



