180 
view generally held that the muscle fibrillae are intracellular, being 
contained in a giant, multinucleated cell. Sections above or below 
the level of the nucleus, however, demonstrate the cell wall comple- 
tely circumscribing the cell protoplasm. The inference seems to be 
justifiable, furthermore, that it is not wanting at the level of the nucleus. 
In torn preparations where the nucleus has been mechanically remov- 
ed from its intimate position in relation to the sarcoplasm, and in 
those other preparations where the nucleus is shrunken, the presence 
of a distinct wall continuous with the remaining portions of the cell 
wall can be detected. It appears not to be an artefactitious product, since 
its outline is regular and definite and it is uniformly and deeply stained. 
Were it due to retracted and shrunken protoplasm we should expect 
to find it irregular in outline, varying in 
aie FR SE Eu thickness, and differing in different levels 
eg Rite) A in intensity of staining. It presents none 
& % ERS Sa 3 * of these artefactitious criterions. Nor does 
| | See) it in any portion of its extent seem to be 
merely the free, unthickened edge of the 
sarcoplasm. It possesses on the contrary 
a definite contour and a definite staining 
reaction. Owing merely to the juxtaposition of the nucleus its out- 
line is overlooked in normal unshrunken tissues. Naturally, therefore, 
at such levels no spongioplasm fibrillae are attached to its internal 
surface. 
The two sketches in figure 1 and 2 are not intended to represent 
exceptional instances in cardiac muscle structure. Such relations 
were observed throughout the entire series of cardiac musculature 
where the conditions were favorable for sharp observation, 1. e., where 
the parts concerned were not obscured by the overlying or under- 
lying by granulae, muscle fibrillae, telophragmata, &e. 
In the study of the telophragmata of this type of muscle no 
instance was observed where these lines traversed either the proto- 
plasm or the nucleus of the muscle cells. This fact may be inter- 
preted as of the following significance. First, it bespeaks the con- 
tinuity of the cell protoplasm and nucleus as appertaining to a distinct 
and individual morphological and functional unit, a cell. Further- 
more, granting the correctness of the observations of numerous 
workers that the telophragmata are always directly and uninterruptedly 
inserted upon the interna] surface of the sarcolemma, we should look 

Fig. 2. 
CO 
