of Pciins!ilrcoi;n, Philadelpliici
T W O FIGURES
F o r many years intercalated disks h a r e been seen in fixed and stained preparations of cardiac iiiuwle cells. I n 1910 Pabezewska, a student of Zimmermaiin, published his method for fixing and staining cardiac muscle wliicli clearly demonstrated their presence. I n 1911 Jordan studied them in liumming bird liearts and in 1912 Jordan and Steele found them in the hearts of a large number of adult rerterbrates. They also examined the hearts of some young rertebrates and found intercalated disks in a 4-pear-olcl child, a 4-clay-old cat, and a guinea pig in the last week of gestation. They found the disks appeared when the cross striations becanie visible.
F o r a long time we have been lookiiig for intercalated disks in our tissue cultures growing in hanging drops but we had not been able to find them. Even the culture which lived to be 180 days old (Hogue, '37) did not show them. It was made from the heart of a n 8-day-old cliick enibq-0.
Recently we have been moye fortunate and have found them when we cultured the hearts of 10-day-old chick embryos aiid grew them in test tubes in a roller-tube apparatus (Gey and Gey, '36) at 37Β°C. The explants were attached to the walls of the test tubes by chicken plasma coagulated with haemostatic globulin. They were bathed with a nutrient fluid made of equal parts of Tyrode Locke-Lewis solution (Hogue, '3'7) and chick embryo extract made up witli the same solutioii 'This research was iiiaterially aided by a grant f m i i the Faculty Research Fiiiid.