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Muscle Fibres and Muscle Cells of the adult White Mouse Heart. 
W. M. Batpwiy. 
(Cornell Medical College New York City.) 
(From the Biological Laboratory at Bonn.) 
With 2 Eigures. 
In two recent publications!) the view was advanced as the result 
of studies upon various voluntary striped muscles, such as latissimus 
dorsi, rectus abdominalis, thigh and leg muscles and extrinsic eye 
muscles of the chicken, cat, calf, white mouse, gray mouse, frog, and 
caudal muscles of the tadpole, that these muscle fibres of the adult 
should not be considered, as we have generally hitherto supposed, as 
large multinucleated cells, but rather as composite contractile struc- 
tures composed of muscle fibrillae and sarcoplasm and containing 
muscle cells. That is to say, each one of the numerous nuclei which 
seem to be immediately imbedded in the sarcoplasm, represents in 
reality a distinct muscle cell, which presents cellular protoplasm com- 
posed of a spongioplasm network with interstices of hyaloplasm and 
which is completely invested by a cell membrane. This. cell mem- 
brane intervenes between the protoplasm of the cell, containing the 
nucleus, and the imbedding sarcoplasm of the muscle fibre. In other 
words, since these same relations hold which all muscle cells, the 
muscle fibrillae and sarcoplasm are extra-cellular structures. Hence 
the generalization usually held, that the adult voluntary striped muscle 
fibre is a multinucleated cell, as stated before, is erroneous. 
Still another fact bespeaking the correctness of these assertions 
was adduced from the studies of the sarcolemma in similar muscles 
and detailed in the second communication. It was found in this 
series that the sarcolemma was a structureless cuticula containing 
neither cells nor fibrils. Everywhere it stood in direct contact with 
the sarcoplasm cf the fibre and afforded attachment to the telophrag- 
mata. Furthermore, its relation to the peripheral-lying muscle cells 
was such, that it was indented into the fibre by the latter, lying, 
therefore, between them and the sarcoplasm and not upon the peri- 
1) Zeitschrift für Allgem. Physiologie (Max Vrrworn) 1912, 
Anat. Anz. Bd. 42. Aufsätze. 12 
