MINUTE ANATOMY OF THE HEART. 247 



this purpose is the nitrate of silver, with subsequent applica- 

 tion of caustic potass, by the employment of which Eberth was 

 able to split up the muscular substance of the heart into sepa- 

 rate prismatic portions, corresponding with the black lines that 

 come into view after treatment with silver, and result from the 

 staining of the connecting substance between the cellular ele- 

 ments. But we may also convince ourselves that, by the ap- 

 plication of other means which render the tissue transparent, 

 the muscular fibres are separated into distinct portions by 

 f highly refractive transverse lines, and that each of these divi- 

 sions contains a nucleus. The want of transparency of the 

 contractile substance usually prevents the delicate boundary 

 lines of the cells from being discerned. But in all experiments 

 in which isolation of the fibres is effected it is possible to 

 obtain small nucleated portions of muscle, presenting similar 

 appearances to those seen in fig. 40, B, the single septal line a 

 being easily distinguishable from a fissure (y) produced by the 

 previous manipulation. 



The limiting surfaces of the several muscle cells are not 

 plane.^ The transverse lines crossing the bundle frequently 

 appear like a flight of steps. Eberth found the borders of the 

 cells more or less regularly dentated. I have, however, ob- 

 served them to be smooth, and believe the difference to be 

 occasioned by the circumstance that the muscle substance 

 sometimes comes under observation in the contracted, coagulated 

 condition, as after treatment with nitrate of silver, and some- 

 times in the swollen, distended condition, as after treatment 

 with acetic acid. Other irregularities of form appear to be 

 due to the pressure which the muscle cells exercise upon one 

 another. Every muscle cell contains a nucleus, occupying a 

 central position, or two or more rarely several nuclei may be 

 found, which sometimes lie in close relation to one another, 

 and are of smaller size, thus appearing to proceed from the 

 division of a single one. If the nuclei be widely separated 

 from one another, the question arises, which it is not 

 necessary here to consider, whether the several nucleated 

 cells represent stages of development, or whether there is a 

 disappearance of the cell wall, or, in other words, that it has 

 become incapable of recognition. In adults the solitary nuclei 



