. The American journal of anatomy . telligible onlyin terms of local modifications (contractions?) at approximatelythe same level in many adjacent fibers. It would seem to rep-resent the morphologic picture of a physiologic state sharplylocalized longitudinally, widespread laterally. In fig. 8 are showntwo series of narrow discs connected by more or less delicategranular inter-disc membranes (risers). These inter-connec-tions, and the localization of the discs in the axial region of themuscular mesh, here again suggest the effect, or phase, of a defi-nite physiologic state. The inter-disc memb
. The American journal of anatomy . telligible onlyin terms of local modifications (contractions?) at approximatelythe same level in many adjacent fibers. It would seem to rep-resent the morphologic picture of a physiologic state sharplylocalized longitudinally, widespread laterally. In fig. 8 are showntwo series of narrow discs connected by more or less delicategranular inter-disc membranes (risers). These inter-connec-tions, and the localization of the discs in the axial region of themuscular mesh, here again suggest the effect, or phase, of a defi-nite physiologic state. The inter-disc membrane may representless extreme local contractions in the intervening fibrillae, or adislocated modified membrane of Heidenhain, or possibly simply anisotropic granules obliquely aligned. Careful focussing revealsthe fact that these complex step-like discs lie superficially through-out and encircle the fiber in ring-fashion. This single observationdisposes definitely of a cell-border interpretation. 158 H. E. JORDAN AND K. B. STEELE. 8 Fig. 7 Longitudinal section of cardiac muscle of bat, showing a granularintercalated disc running across eight fibers. Fig. 8 Heart muscle of bat showing two long step-like discs winding super-ficially around their fibers. The risers probably represent anisotropic granulesaligned longitudinally, or perhaps a distorted membrane of Heidenhain. INTERCALATED DISCS OF HEART MUSCLE 159 3. Guinea-pig Fig. 9 illustrates the typical condition in adult discs are again aggregated in more or less definite areas;they may be wide or narrow, delicate or robust, compact or looselygranular. At the left, two discs are shown connected by a rowof granules; a similar disc, of mono-serial coarse granules, ex-tends uninterruptedly across the two middle fibers. The samecondition, producing the disc-structure, prevails at approxi-
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1912
