200 On the Construction of the 



IV. — On the Construction of the Bark or Double-bordered Nerve 



Fibre. By Dr. H. D. Schmidt, of New Orleans, U.S.A. 



Plates LX., LXI., and LXII. 



During a period of four years, beginning in the autumn of 1868, 

 the greater part of my attention was devoted to microscopical 

 researches into the structure of the nervous tissues. Of these re- 

 searches, the subject of the present treatise, the double-bordered 

 nerve fibre, forms a part. 



The results obtained from these investigations, however, do not 



EXPLANATION OF PLATES LX., LXI., AND LXII. 



Fig. 1, Pl. LX. — Peripheral nerve fibres of the frog, examined in serum ; a 

 and b, of the living, c of the recently killed, showing indentations of the double 

 contour. Magnf. 500 diam. 



Fig. 2, Pl. LX. — Peripheral nerve fibre of the mouse, prepared in serum im- 

 mediately after death and subsequently treated with water. This fibre sliows the 

 fine dark line within the double contour. Magnf. 720 diam. 



Fig. 3, Pl. LX. — Fresh peripheral nerve fibre of man, examined in water, 

 showing the sack-like bulgings and corresponding windings of the delicate fibrils 

 of the fibrinous layer. Maguf. 720 diam. 



Fig. 4, Pl. LX. — Fresh peripheral nerve fibre of man, examined in water. On 

 its open end, a portion of the fibrillous layer is seen to escape in loop-shaped 

 bundles, showing distinctly their fine fibrillous character. On the side of the 

 nerve fibre, the fibrillous mass is seen to escape through a minute rent in the 

 tubular membrane in the form of a hernia. A considerable portion of the fibril- 

 lous layer has already escaped from the nerve fibre, in consequence of which 

 the wavy fibrils crossing each other here and there appear very distinct. Magnf. 

 720 diam. 



Fig. 5, Pl. LX. — Peripheral nerve fibre of the mouse with dilatations, ex- 

 amined in water immediately after deatli. Magnf. 720 diam. 



Fig. 6, Pl. LX. — Fresh peripheral nerve fibre of the mouse, examined in water. 

 In the interior of the fibre, the fibrillous bundles forming loops and covered by the 

 semi-liquid medullary layer, characterized by its fatty lustre, as well as a number 

 of single fibrils, all moving toward the open end of the nerve fibre, are seen. On the 

 side we observe the fibrillous layer, a considerable portion of which has already 

 been removed by the endosmotic current of the water at the lower end of the 

 fibre. ]\Iaguf. 720 diam. 



Fig. 7, Pl. LXI. — a and b, loop-like fibrillous bundles covered by the medul- 

 lary layer, which escaped from the same nerve fibre. Magnf. 720 diam. 



Fig. 8, Pl. LXI. — Frosh peripheral nerve fibre of the mouse, prepared in 

 glycerine and subsequently treated with water. A portion of the fibrillous layer 

 is here seen to escape from the open end of the fibre, in the form of fine fibrillous 

 bundles, even single fibrils, all forming loops. The inner space of the latter is 

 only filled by a very thin portion of the medullary layer, in consequence of which 

 the individual fibrils appear very distinctly in this specimen. Magnf. 720 diam. 



FiG. 9, Pl. LXI. — Peripheral ntrve fibre of the same animal in glycerine. 

 Magnf. 720 diam. 



Fig. 10, Pl. LX. — The same nerve fibre, swollen by a subsequent treatment 

 with water. 



Fig. 11, Pl. LXI. — Nerve fibre of tlie same specimen with a hernia. 



Fig. 12, Pl. LXI. — Fibrillous loops and coils ; a, loops escaped from the pre- 

 ceding fibre (Fig. 11), and covered by a thin portion of the meduUary layer ; b and 

 c, fibrillous coils, on which the medullary covering was partially dissolved by the 

 action of water. 



Fig. 13, Pl. LX. — Peripheral nerve fibre of the alligator, taken from a nerve 

 having remained twenty-four hours in a solution of chromic acid; a, the entire 



