611 
from pigs of the following lengths: 10 mm, 13, mm, 15 mm, 20 mm, 
26 mm, 35 mm, 44 mm, 55 mm, 72 mm, 84 mm and 100 mm. 
Various methods of preparation were employed, although that princi- 
pally used was the method proposed by Korossow !) for the demon- 
stration of protoplasmic bridges in endothelium etc. The tissues were 
hardened in osmic acid and subsequently treated with a reducing 
mixture, made up of solutions of pyrogallic and tannic acids. 
Specimens were also prepared by the ordinary methods of har- 
dening such as absolute alcohol, ZENKER’S fluid etc., and stained in 
haematoxylin und eosin, in acid fuchsin and picric acid, and in 
safranin. 
Frozen sections and fresh teased preparations were also studied. 
Sections were cut in both celloidin and paraffin. 
Appearances met with in Adult Heart Muscle. 
Human heart muscle. The outline of the cell is irregular, 
but speaking generally it is rhomboidal in longitudinal sections, the 
length being three or more times the width. The cells often break 
up into branches, which join with branches from other cells to form 
a sort of network. The band of demarcation between the cells is 
placed at an acute angle to the long axis of the fibre, and in the 
human subject has quite a complex structure. As represented in 
Fig. 1 the fibril bundles each break up into two or three small fila- 
ments which extend across the space to meet those from the cell 
opposite. In the centre of the space there is a narrow deeply staining 
line of separation, up to which the filaments run on both sides. This 
confirms the findings of PrzEwoskı?) who has described a similar 
structure as characteristic of human heart muscle. On each side of 
the clear band of separation, there is a narrow more deeply staining 
region which Przewoskı has called the stratum granulosum terminale. 
These characters can be made out in specimens stained by any of 
the ordinary methods, such as haematoxylin and eosin, but are most 
distinct in those treated by Korossow’s method, although they are 
almost equally plain in acid fuchsin and picric acid preparations. 
In none of my specimens from other animals have I been able 
1) A. Korossow, Ueder eine neue Methode der Bearbeitung der Ge- 
webe mit Osmiumsäure. Zeitschr. f. wissenschaftl. Mikroskopie, Bd, 9, 
1892, p. 38. 
2) M. Przewoskı, Du mode de réunion des cellules myocardiques de 
Vhomme adulte. Archives des sciences biologiques de St. Pétersbourg, 
Tome 2, p. 287. 
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