544 DEVELOPMENT OF THE SIMPLE TISSUES, BY S. STRICKER. 



to the naked eye, though they are often very much smaller ; 

 in short muscles they are equal in length to the muscle itself, 

 but in long muscles they do not in general exceed four centi- 

 meters (about one inch and three-quarters). 



Schwann discovered a sheath investing the fibres, which 

 he termed the sarcolemma, and since his time it is customary 

 to say that the sarcolemma is completely filled with the true 

 muscular substance. The sheath cannot be seen in fresh fibres, 

 but it comes into view when they are treated with water or 

 diluted acetic acid, or, in short, with any reagent that exerts no 

 action upon the sheath, but causes the muscular substance to 

 swell. The sheath ultimately ruptures at some point, the 

 muscular substance protrudes, and the ruptured canal of the 

 sheath then comes distinctly into view. In such preparations, 

 especially if the muscle examined be not fresh, but have been 

 dead for about twenty-four hours, we may sometimes succeed 

 in exhibiting considerable portions of the sheath : it then 

 appears as a very thin, extremely transparent, and as seen with 

 our instruments, structureless membrane. 



Schwann also discovered the nuclei of the muscular fibres ; 

 these are the muscle corpuscles of authors ; and from the exact 

 investigation of these, Max Schultze, as is well known, was led 

 to make the first steps towards the reform of the old doctrines 

 regarding cells. 



The muscle corpuscles lie for the most part on the surface of 

 the muscular substance between this and the sarcolemma. 

 Bonders* found that in the muscular fibres of the heart the 

 muscle corpuscles occupied the interior of the fibre. Rollettf 

 has further shown that muscle corpuscles are met with in 

 the interior of the substance of the fibres of the muscles in 

 Amphibia, Fishes, and Birds. 



Schwann, lastly, demonstrated the fibrils of muscular tissue, 

 which he described as moniliform threads. He attributed the 

 peculiar appearance on account of which these fibres are 

 termed transversely striated to the regular collocation of the 

 thicker and thinner parts of these fibres. For if such a fibre 



* Physiologie des Menschen, German translation by Theile. 

 t Wiener Sitzungsberichte, 1857. 



