96 
Dr. Beale^ on Sarcolemma. 
formed elementary fibres, it is not to be demonstrated as a 
distinct tube in the case of tlie young elementary fibres of 
the same muscle, 
THE FORMATION OF SARCOLEMMA. 
Of the masses of germinal matter {nuclei^) in relation with 
striped muscle. — In considering the development of muscular 
tissue, and other structures connected with it, it must be 
borne in mind that several tissues of very different nature 
are undergoing development at the same time, and in very 
close relation with one another, and that the apparent 
confusion often observed in specimens is in great measure 
due to the number of nuclei which take part in the formation 
of these different textures. Even at a very early period of 
development of muscular tissue nuclei of more than one kind 
can be clearly recognised, and have been figured by some 
observers. But I am not aware that any one has succeeded 
in following out the changes which these several kinds of 
nuclei undergo, or in demonstrating the precise part they 
play in the production of the tissues which undoubtedly exist in 
the fully formed muscle, but which cannot be recognised at an 
early period of development. There are at this early period — 
(PL XIV, fig. I) nuclei which take part in the formation of the 
muscular fibres; (fig. 2) nuclei concerned in the development of 
vessels ; (PL XV, fig. 3) nuclei concerned in the development 
of nerves. The last two series of nuclei are generally sepa- 
rated from the first by the thickness of the contractile tissue 
produced ; but in some cases, in consequence of the produc- 
tion of muscular tissue taking place on one side only of 
the muscular nuclei, the latter are in such cases very close to 
the nuclei of the vessels and nerves. In the muscles of insects 
a vast collection of nuclei are sometimes seen upon the sur- 
face of the muscular fibres. These nuclei are concerned in the 
development of the tracheae and of the nerve -fibres ; but at 
this early period these structures are so exceedingly transpa- 
rent that no distinct fibres, or, indeed, any form of structure 
can be traced between the several nuclei, and it is necessary, 
in order to ascertain the meaning of the appearances observed, 
to examine muscular fibres of animals of the same kind at 
different ages. The various stages of development of the 
nerves and trachese may be very clearly made out in the 
* I use the term " nucleus" in a general sense only. The ordinary name 
by which these masses of living or germinal matter of the muscle are known 
is " nuclei/' for which reason only I use it here. 
