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sarcolemma than under it, though at times a knob could be observed to penetrate deeper towards the fibrillated sarcous substance. It was noted that in every ending the fibrillated sarcous substance was sharply marked off, so that it was always easy to determine that the nerve terminals did not penetrate within or even as far as the fibrillated muscle substance.

On the ultraterminal fibrillae a sheath could at times be seen. This sheath followed closely the convolutions of the nerve, and could be traced to the neighboring muscle to which the nerve was going; there it blended with the sarcolemma. The nerve terminals and end-knobs differed in no respect from the corresponding parts of the main nerve stem (Fig. 6).

In short the primary divisions of the nerve ending lie over the sarcolemma, and are surrounded by both the neurilemma and the sheath of HENLE; the ultimate fibrils lie in a homogeneous substance within the sarcolemma, and are covered by a cap formed by the blending of these sheaths with the sarcolemma. The open condition of the sheath of HENLE, as described. by SIHLER, was not observed.

Conclusions.

The so-called nerve ending of the frog is to be regarded in the first place as the peripheral separation of the contents of the axis cylinder, by which separation it is able to spread itself over a relatively wider area. As a nerve fiber may attach itself to various muscle fibers, so the fibrillae of the ending may likewise reach over to ådjacent muscle fibers. Those fibrils which detach themselves near the central point of separation are, as a rule, larger and more easily stained than the more distal ones, and are comparable to the non-medullated fibers which may arise from the medullated nerve stem. One can note that the secondary endings to which they give rise are often comparable in form to the primary endings, though having a smaller number of branchings; this would suggest that the amount of branching which is possible bears a relation to the diameter of the fiber.

A plexus is often formed by the nerve terminations (Fig.

may become.

5, Fig. 3, Fig. 6.). Whether this is merely an interlacing or a true anastomosis, it would be difficult to decide. The close approximation of some of the terminals and the way in which they run together (Fig. 6) suggest at least a very intimate relationship between them. By means of this plexus arrangement we can well understand how effective the nerve impulse

From this network fibrillae may pass to other muscle fibers (Fig. 3, Fig. 6).

Not only in the fixed but in the unfixed preparations the larger branches of the endings are seen to lie over the sarcolemma and even at some distance from it (Fig. 1, Fig. 7). In fresh preparations one occasionally sees a terminal lying over the paler stained yet clearly outlined muscle fiber, and sending down root-like structures to the muscle fiber. The neurone enters into intimate relationship with the muscle fiber either at the peripheral termination of the ending, where each termination appears as a very fine fibrilla to which an end knob or bulb may be attached (Fig. 1, B & C, Fig. 9) or at the terminal knob of each of those root-like structures which at times are projected from the fibrils of a nerve ending. The former termination, including both the terminal fibrilla and its knob, lies in homogeneous substance under the sarcolemma; it is covered by a cap into whose formation there enters both the nerve sheath and the sarcolemma, though chiefly the nerve sheath. The latter termination is in close opposition to the sarcolemma and may be either in or under it.

BIBLIOGRAPHY. Apathy, St. v.

Kontraktile und leitende Primitivfibrillen. Mitteil. d. zool. Stat. zu Nea.

pel, 1892, Bd. 10, 355-375. Das leitende Element in den Muskelfasern von Ascaris. Arch. f.

mikr. Anat., 1904, Bd. 43, p. 886-911. Das leitende Element des Nervensystems und seine topographischen

Beziehungen zu den Zellen. Mitteil. d. zool. Stat. zu Neapel, 1897,

Bd. 12, p. 495-748.
Ueber Neurofibrillen. Proc. of the inter. cong. of zool., Cambr., 1898,

Sep.

M. Heidenhain's und mein Auffassung der kontraktilen und leitenden

Substanz und über die Grenzen der Sichtbarkeit. Anat, Anz., 1902.

Bd. 21, p. 61. Barker, L. F.

The Nervous System and Its Constituent Neurones. New York, 1899. Bethe, A.

Eine neue Methode der Methylenblaufixation. Anat. Anz., 1896, Bd. 12,

p. 438.

Die anatomischen Elemente des Nervensystems und ibre physiologische

Bedeutung. Biolog. Centralbl., 1898, Bd. 18, p. 843-974.

Allegemeine Anatomie und Physiologie des Nervensystems. Leipz., 1903. Cuccati.

Delle terminazioni nervee nei muscoli addominali della Rana temporaria

e della Rana esculenta. Internat. Monatsh. f. Anal. u. Phys.,

1888, V. Dogiel, A. S.

Methylenblautinction der motorischen Nervenendigungen in den Mus

keln der Amphibien und Reptilien. Arch. f. mikr, Anat., 1890,

XXXV. Ehrlich, P.

Ueber die Methylenblaureaktion der lebenden Nervensubstanz. Biolog.

Centralbl., 1887, Bd. 6, p. 214-224.
Ueber die Beziehungen von chemischer Konstitution, Verteilung und

pharmakologischer Wirkung. v. Leyden- Festschrift, 1901, Bd. I, Sep. Gerlach.

Ueber die Einwirkung des Methylen blaus auf die Muskelnerven des

lebenden Froschen. Sitzber. d. math.-Phys. Cl. d. k. bayer. Akad. d.

Wiss., 1889, XIX. Grabower.

Ueber Nervendigungen im menschlichen Muskel. Arch. f. mikr. Anat. u.

Entwickl., 1902, Bd. 60, I. Kühne.

Ueber die peripherischen Endorgane der motorischen Nerven Leipzig,

1862. Krause.

Uber die Endigung der Muskelnerven. Arch. f. rat. Med., 1863. Also

several papers in the earlier numbers of the Internat. Monatsh. f.

Anat. u. Phys. Huber-DeWitt.

A Contribution on the Motor Nerve-endings and on the Nerve-endings

in the Muscle-spindles. J. Comp. Neur., 1897, v. 7, 169-230. Perroncito, A.

Sur la terminaison des nerfs dans les fibres musculaires striées. Arch.

Ital. de Biol., 1901, 36, 245-254. Ruffini, A., and Apathy, St.

Sulle fibrille nervose ultraterminali nelle piastre motrici dell'uomo.

Riv. di Pat, nerv. e ment., Firenze, 1900, v. 5, 433, Sep.

Ruffini, A.

Le fibrille nervose ultraterminali nelle terminazioni nervose di senso e la

teoria del neurone. Riv. di Pat, nerv. e ment., 1900, v. 6, 70-82. Sihler, Chr.

Neue Untersuchungen über die Nerven der Muskeln mit besonderer

Berücksichtigung umstrittener Fragen. Zeit. f. wiss. Zool., 1900,

LXVIII, 3, pp. 323-378.
The Nerves of the Capillaries, with Remarks on Nerve Endings in Mus-

cle. Journ. of Experimental Medicine, 1901, vol. 5.

EXPLANATION OF THE DRAWINGS. I am much indebted to Mr. LEONARD H. WILDER for the carefulness and accuracy with which he has prepared the drawings which illustrate this paper.

PLATE I.

Fig. 1. Zeiss D, Comp. occ. 4. The peripheral termination of a neurone, showing Terminal fibrillae with end knobs (1) and (2), Ultraterminal fibrilla ending in intermuscular counective tissue (3), Ultraterminal fibrilla ending on a separate muscle fiber (4).

The medullary sheath, as sometimes happens, is faintly yet distinctly outlined surrounding the continuous and well-marked axis-cylinder. There are three muscie fibers, A, B and C, to which go two medullated nerves, a and b. The main stem of a breaks up on C at 5 into three primary fibrils. In its course there are given off to A two medullated branches, which lose their medullary sheath soon after leaving the main stem and which break up more or less dichotomously. From the one on the left, a non-medullated terminal branch (3) passes beyond the muscle fiber to disappear in the intermuscular connective tissue. The main supply of B is b; but the medullated nerve, a, while passing over B gives off two very fine, apparently non-medullated branches, one of which ends on B, the other passing to end on C. The termination of the medullary sheath of a was close to the breaking up of the axis-cylinder at 5. One the primary terminal branches on the right gives off a branch 4 which divides dichotomously on muscle fiber B. The others call for no special remark.

Fig. 1, B and C. Zeiss 1.12 oil immersion ; Comp. occ. 4. Two forms of endings frequently presented at the terminals of very fine fibrillae.

B. Drawn from (1), shows the fibrillae breaking up into a granular net. like structure.

C. Drawn from (2), shows an elongated broadened club-like body with a marked central axis, imbedded in a well-defined granular mass and surrounded by a homogenous capsule, comparable to cap seen in Fig. 9.

Fig. 2. ZEISS D, Comp. occ. 4. Nerve ending with ultra-terminal fibrillae.

The medullated nerve a loses its medullary sheath and breaks up on B at (1). It gives off at (2) a large non-medullated branch which also breaks up on B. The nerve endings send ultraterminal fibrillae to three muscle fibers. The terminal branches to the right could be traced to a distance twice as far as represented. Several of these endings showed knobs similar to those repre

sented in Fig. 1, B and C. A separate non-medullated nerve (n) is shown which forms a small plexus on B, one fiber of which penetrates to a lower plane than the others and ends by forming under the sarcolemma a knob like Fig. 1, B; the other fibers pass on, one to end on B, the other on C.

Fig. 3. ZEISS D, Comp. occ. 4. Three medullated nerves (a), (b) and (c), which pass to three separate muscle fibers, A, B and C, and which have ultraterminal fibrillae and interlacing of endings. Muscle fiber B is seen only in part.

Fig. 4. ZEISS D, Comp. occ. 4. The type of ultraterminal fibrillae seen most frequently.

Fig. 5. A. ZEISS D. Comp. occ. 4. An ending forming a complex network on muscle fiber C. A nerve coiling round the primary terminal divisions of another nerve (compare page 11 on relation of nerve to sarcolemma). The nerve n goes to two muscle fibers, A and C. The nerve 3 on which no medullary sheath was seen divides into two branches; one of these ends undivided, the other separates into two branches which run close together and parallel. At (2) the upper branch coils round a primary fibril of the nerve ending on muscle fiber A; in addition it gives off a fibril which disappears in adjoining connective tissues.

Fig. 5, B. Part of Fig. 5, marked (1), drawn with ZEISS oil immersion 1-12 Comp. occ. 4.

PLATE II.

Fig. 6. ZEISS 1-12 oil immersion, Comp. occ. 4. Sections cut 10 μ. Nerve endings shown only in part, with ultraterminal fibrillae (1), (2) and (3), one of these (1) with sheath. The main fiber is seen at n. From it a branch to the right passes off and soon divides; one of these divisions has been cut by the sectioning, the other (1) passes to an adjoining muscle fiber, there to end in a small termination like an end-plate with end knobs. The nerve sheath could only be traced distinctly to the point where the nerve enters into contact with the muscle fiber.

Fig. 7. ZEISS 1-12 oil immersion, Comp. occ. 4. Section 5 μ. Stained in orange G, acid fuchsin. Part of nerve ending lying over sarcolemma. This dye colors the sheath of HENLE rose-pink, the neurilemma pink, and the muscle fiber orange. The medullary sheath was apparent at M just above the node R, where the axis-cylinder divides into three branches which pass to the muscle fiber. The sheath of HENLE (H) is seen continued over R wituout attachment, and two of its nuclei (Hn) were distinctly outlined. Within the sheath of HENLE and closely applied to the axis-cylinder, lay the neurilemma N, attached to the node R. The primary terminal fibrils surrounded by the sheaths lie over the sarcolemma which is distinctly marked beneath the sheath. Fig. 8. ZEISS apochomatic 1.5, Comp. occ. 6. Section 7.5 μ. A primary terminal fibril with sheaths. H, HENLE'S sheath; N, neurilemma; S, sarcolemma.

Fig. 9. ZEISS apochromatic 1.5, Comp. occ. 6. Section 5u. A terminal knob lying under the sarcolemma and covered by a cap which is chiefly composed of the nerve sheath. Fine fibers pass at (a) and (b) from the sarcolemma to blend with the nerve sheath in the cap.

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