Harry Lewis Wieman 193 
Besides section methods, maceration was employed. This process was 
used with satisfactory results in studying the general structure of the 
entire cell of the adult tissue. Of the various methods tried, treatment 
for twenty-four hours with a 20 per cent solution of nitric acid, fol- 
lowed by staining with Delafield’s hematoxylin and acid fuchsin, gave the 
best preparations. 
THe ApuLtt Herart-Muscie CELL. 
Examination of the adult tissue shows it to be composed of an anas- 
tomosing network of fibers, the demarcation of which into cells is rather 
uncertain. Apparently a fiber is arranged into cylindrical cells the 
length of which exceeds many times the diameter. The tapered ends 
of the cells seem to fit together much in the manner of a dove-tailed . 
joint. The nucleus is oblong in shape and occupies a more or less central 
position, although it is sometimes seen very close to the periphery of 
the fiber. 
The contractile substance, the fibril bundles, consists of deeply staining, 
longitudinal masses running the length of the cell. Surrounding the 
fibril bundles and separating each one is the undifferentiated sarcoplasm. 
Fig. 15 represents portions of two fibril bundles, each with its envelope 
of sarcoplasm, from the outer wall of the ventricle of the adult fowl. 
The fibril bundles are divided by cross striations at right angles to the 
longitudinal axis into alternating broad, deeply staining bands, and 
narrower bands more lightly stained (Fig. 15, b/). The broad, heavily 
stained bands correspond to the “ Querscheibe,” or “ Briicke’s doubly 
refractive substance” of mammalian heart muscle (MacCallum, 97). 
One of these bands is shown in Fig. 15,a. By carefully focussing up 
and down, a very narrow, deeply staining band can be seen crossing the 
light bands. This is the “ Zwischenscheibe,” or “ Krause’s membrane,” 
which structure is not very distinct nor readily made out. The con- 
tinuation of this line, however, can be plainly seen in the sarcoplasm 
surrounding the fibril bundle (Fig. 15, c). The Querscheibe, as is readily 
shown in Fig. 15, are slightly larger in diameter than the more lightly 
stained parts between. 
The sarcoplasm surrounding the fibril bundles is not homogeneous, 
but is divided into disc-like parts (Fig. 15,d), which could be especially 
well seen in peripheral cells when partially macerated. In preparations 
of this kind, the discs were found separate from each other, while the 
fibril bundles remained intact, that is, they did not break up into corre- 
sponding lengths. This it seems would militate against the idea of 
