334 LUCILE WITTE 
Other methods of staining were used with no success at dif- 
ferentiating the discs. The iron-hematoxylin method was used 
on the earlier tissues with no results and the Delafield’s hema- 
toxylin with an eosin counterstain was used on the older tissue 
where the dises are known to exist, with equally unsuccessful 
results. The striations, however, were very evident. 
HISTORICAL REVIEW 
Zimmerman,! Palezewska,? and Werner® in 1910 worked out 
very complete studies of adult human and mammalian heart 
muscle with regard to the function of the intercalated discs 
and they all concluded definitely that the dises did form distinct 
cell boundaries. Palezewska, in her work on the human heart, | 
evolved some diagrams (figs. 2, 9, and 10) which at first glance 
would seem very convincing. However, on closer study, they 
cannot be accepted. H. E. Jordan‘ has reviewed both Pal- 
ezewska’s and Werner’s papers in his study of the heart muscle 
of the humming-bird, and the reader is referred to his paper 
for a more detailed review. Werner, in making her study of 
the mammals, worked out the cardiac muscle of the adult pig 
quite thoroughly, and she noticed a striking peculiarity which 
was that the nuclei of the ‘muskelterritorien’ tended to range 
themselves in long rows, numbering in multiples of from 2 to 
32, though the most usual number was 8. The intercalated 
dises seemed to divide these series of nuclei into distinct cells, 
as her figures 1, 2, 3, and 4 show. She compared the ventric- 
ular muscles with those of the auricles and found that the nuclei 
were not nearly so numerous in the auricles ranging usually 
+n number from 1 to 2 and 4. The discs occurred in zigzag lines 
in both ventricle and auricle. 
Concerning the structure of heart tissue, Jordan* stated briefly 
that in the humming-bird the muscle ‘‘is syncytial in character, 
the fibers anastomosing laterally and apically.” A distinct 
membrane or sarcolemma existed and seemed to cover the en- 
tire fiber. 
J. B. MacCallum,® in his study of the histogenesis of heart 
tissue, used the pig embryo in a series of from 10 to 100 mm. 
