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A. To scale reconstructions, showing the dorsal halve of the heart.. B. Cardiac profiles during development, arbitrarily fixed at the right margin of the atrioventricular canal. C. The ventricle is initially wider (right-left) and deeper (dorsal-ventral) than long (caudal-cranial), but growth is primarily by lengthening. avc, atrioventricular canal; l(r)a, left(right) atrium; sv, sinus venosus; ven, ventricle.
