At the center of the sarcoplasm is seen a blood capillary (cp) filled with
red corpuscles (re) quite comparable with those shown in a neighbor-
ing capillary (re). This figure proves that the invading tissue may
sometimes assume the form not of a septum but of a rounded cord or
at least a kind of vascularized papilla following the axis of the cylin-
drical cell. Jordan and Banks (1917) draw attention to a similar
feature in their Fig. 42 where " an artery appears to be within the
cell. This definitive condition is probably the result of a secondary
adaptation of the cell to the growing bloodvessel " (p. 305) . From the
above description it follows that the Purkinje cells of the normal
heart possess quite a special morphology. No other tissue shows stages
so varied as regards the distribution of the nuclei, the transformation
from a unipartite element into a bipartite or multipartite element, or
the consequent division of the cell body. These stages really represent
a series of successive phases which terminate in the longitudinal
cleavage of a mother-cell into smaller and simpler daughter-cells. The
subdivision is provoked or at least accompanied by a proliferation and
extension of the neighboring vascular perimysium.
