. Bulletin of the Bureau of Fisheries. Fisheries; Fish culture. 54 BULLETIN OF THE BUREAU OF FISHERIES. MUSCLES OF THE DORSAL FIN. Harrison " has briefly described the muscles of the dorsal fin of Salmo salar in con- nection with his study of the development of the fins of teleosts. The muscles in the king salmon are similar in character and arrangement. The number of dorsal fin rays is greater in Oncorhynchus tschawylscha than in Salmo salar. The muscles of the fin have a correspondingly greater number of divisions, one for each fin ray. A typical fin ray is moved by three pairs of muscl
. Bulletin of the Bureau of Fisheries. Fisheries; Fish culture. 54 BULLETIN OF THE BUREAU OF FISHERIES. MUSCLES OF THE DORSAL FIN. Harrison " has briefly described the muscles of the dorsal fin of Salmo salar in con- nection with his study of the development of the fins of teleosts. The muscles in the king salmon are similar in character and arrangement. The number of dorsal fin rays is greater in Oncorhynchus tschawylscha than in Salmo salar. The muscles of the fin have a correspondingly greater number of divisions, one for each fin ray. A typical fin ray is moved by three pairs of muscles, (i) an inclinator, (2) an erector, and (3) a depres- sor. Beside, the fin as a whole is moved forward by the pair of protractors and back- ward by the pair of retractors described with the group of longitudinal muscles. The specific fin muscles may be described more fully as follows: INCLIN.\TOR DORSALIS (THE SUPERFICIAL '^L MUSCLE OF MCMURRICH). This muscle in reality consists of a series of short muscles, i. e., independent slips, corresponding in number with the dorsal fin rays. Each tiny slip has its origin in a fascia which is strongly attached to the skin and which covers the dorsal margin of the great lat- eral muscle. The fibers of each muscle slip converge as a conical mass ending in a short tendon inserted into the postero-lateral margin of the base of each fin ray. These muscle slips are about 20 mm. long in the ante- rior members of the series and 15 mm. in the posterior. The extreme anterior three or four slips are very rudimentary and may readily be overlooked in the dissection. There are 13 free slips, 16 or 17 in all. In the sea form the spaces between muscle slips are filled with subcutaneous fat. The ends of the deep fin muscles are to be seen just between the ends or insertions of the inclinator slips. Harrison was the first to describe these muscles carefully, and to him we owe the name' '; The contractions of the divisions of the
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