CHAP. VII.] 



THE SARCOLEMMA. 



155 



In fig. 39 is represented the border of some 

 fibres, from which several of the sarcous elements 

 have been removed accidentally by maceration in 

 weak spirit. The remaining ones project in lateral 

 series, evincing their adhesion to one another in 

 that direction, and the non-existence of any spiral 

 arrangement. 



The size of the particles composing the fibre 

 may be measured in one direction by the trans- 

 verse stripes formed by their union. 



The following average, deduced from nume- 

 rous observations, shews great uniformity in this 

 respect. 



Eng. In. 



In the Human subject 5355 



Mammalia generally TOSM 



Birds T5755 



Keptiles TT i(5o 



Fish Tnjjg 



Insects gs'sa 



Fig. 39. 



No. of 

 Observations. 



...27 



7 

 7 



20 

 8 



In the opposite direction, or that marked by the distance be- 

 tween the longitudinal dark lines of the fibre, their diameter is less, 

 often by one half. It is important to remark, that these measure- 

 ments are taken from uncontracted specimens, since during con- 

 traction the relative diameters of the particles are changed. 



Of the Sarcolemma. The striped fibre is enclosed in a tubular 

 sheath or sarcolemma^ adapted to its surface, and adhering to it. 

 This consists of a transparent, very delicate, but tough and elastic 

 membrane, which isolates the fibre from all other tissues. In 

 general, it has no appearance of any kind of structure ; but in the 

 case of bulky fibres, where it is strong in proportion, faint indica- 

 tions may be detected of a com- 

 plex interweaving of filaments far 

 too minute to be individually re- 

 cognised. It occasionally has 

 small corpuscles, the remains of 

 cell-nuclei, in contact with it. 



This membrane may be 



Fig. 40. 



Seen forming a transparent - Fragments of an elementary fibre of the Skate 

 ii ,i f\ -i 1,1 ' 1C ' (1 together by the untorn but twisted sarco- 



border to the fibre beyond the lemma 



