Legend to Supplementary Material
Supplemental Movie 1.Activation spreading through a looped tubular heart of chick
embryo at Stage 13 (approximately embryonic day 2.5). Note the rather slow, almost
isotropic spread of excitation along the cardiac tube.
Supplemental Movie 2. Alternation of rapidly (atrium and ventricle) and slowly
(atrioventricular canal and outflow tract) conducting segments is a characteristic feature
of the period of chamber formation. Another slowly conducting segment, sinus venosus,
is not visible due to its posterior location. Stage 17 (embryonic day 3) chick heart. A
static version (Montage) of this movie appeared in Reckova et al. 25.
Supplemental Movie 3.Illustration of beating of Stage 24 (embryonic day 4) chick heart.
Green illumination is used to maximize contrast of blood. Due to the heart’s superficial
location and tissue transparency, atrial and ventricular volumes and other functional
parameters can be derived from this recording akin to angiography used in clinical
settings. A wealth of information about embryonic cardiovascular system was obtained
using this technique by Clark and associates 38; currently, such a fully digitalized imaging
setup can be obtained for less than $1,000 .