. Anatomischer Anzeiger. Anatomy, Comparative. 247 in the distal portion of the muscle, well defined macroscopic units, each about half-a-centimeter wide and a millimeter thick, which extend from the costal to the distal margin of the muscle and terminate at each end in a well marked tendon (Fig. 4a). Nerves of innervation enter bundles of this kind at several places, as shown at the right in the figure. After maceration in the nitric-acid-glycerine mixture above men- tioned it is easy to isolate small fibre-bundles, less than half-a-milli- raeter in diameter, which run completely across the m
. Anatomischer Anzeiger. Anatomy, Comparative. 247 in the distal portion of the muscle, well defined macroscopic units, each about half-a-centimeter wide and a millimeter thick, which extend from the costal to the distal margin of the muscle and terminate at each end in a well marked tendon (Fig. 4a). Nerves of innervation enter bundles of this kind at several places, as shown at the right in the figure. After maceration in the nitric-acid-glycerine mixture above men- tioned it is easy to isolate small fibre-bundles, less than half-a-milli- raeter in diameter, which run completely across the muscle. In a series of cross-sections taken through a secondary segment, it is not, how- ever, possible to follow any given group of fibres from one extremity of the segment to the other. The disposition of the connective-tissue is far too irregular to admit of this. The small fibre-bundles isolated after maceration are therefore to be looked upon as artificial secondary units, the muscle-fibres themselves being the primary units. By carefully teasing one of these small bundles of fibres the in- dividual fibres composing it may be isolated. When this is done it is found that none of the individual fibres run the entire length of the Fig. 4. a Macro- scopic "unit" isolated from the distal portion of a human external oblique muscle, b In the center is shown a flat band of fibres dissected from the external oblique muscle of a dog. The main nerve trunks crossing near this band are represented by the broad dark lines. The areas of distribution of mo- tor nerves to the muscle- fibres composing the band are shown by groups of dots. At each side a few isolated muscle-fibres are shown. For the sake of clearness they are repres- ented disproportionately wide. One-half natural size. Fig. 5. The ex- ternal oblique muscle of a dog. The main nerve trunks only are shown. The areas of innervation of two flat bands of fibres a-b, c-d are represented by groups of clots. Two- fifths nat
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