302 H. E. JORDAN AND J. B. BANK.^ 



trabeculae. These conditions, combined with the less difier- 

 entiated character of tlie nuclei, the form of the muscular mesh, 

 and the prevailing form of the discs, all indicate a relatively less 

 highly differentiated musculature. The sarcolemma also is 

 more generally festooned (figs. 29, 32, 33 and 34). The telo- 

 phragmata are in intimate union with both the sarcolemma and 

 serrations of the nuclear membrane (fig. 34). There is not the 

 sUghtest indication in any condition of an additional mem- 

 brane, the alleged mesophragma (Heidenhain). Since its pres- 

 ence can not be demonstrated in the relatively coarse muscula- 

 ture of the beef heart, its occurrence in cardiac muscle seems 

 doubtful. 



The discs are generally of the narrow band-type, in close as- 

 sociation with telophragmata (figs. 29, 31, 32 and 33). Step- 

 forms occur,' but connecting membranes ('risers') appear to be 

 lacking. There is some evidence of persisting amitotic divi- 

 sion of the nuclei in this region. The moderator band here de- 

 scribed is relatively slender, and the heart is that of a young, 

 almost full-grown, beef. 



The musculature of the moderator band furnishes an excep- 

 tionally favorable opportunity for testing the conclusion that 

 discs occasionally lie superjacent to the nuclei. The difficulty 

 of establishing this fact in tissues where abundant branches arise 

 from all surfaces of a main cylindric trabecula is fully appreci- 

 ated. But the illustrations given in support are of examples 

 where no doubt can remain (figs. 6, 7, 8 and 9). The fact is, if 

 possible, still more certain in figure 31; here the supernuclear 

 group of discs has no relation to anastomoses with extraneous 

 branches. Identical evidence accrues also from a study of 

 teased preparations. Finally, the group of discs shown in figure 

 31 admits of no interpretation except in terms of a supernuclear 

 location within the 'cell-area' represented by this nucleus. 



The possible suggestion that the discs represent an original 

 intercellular substance (plus apposed cell-membranes), into which 

 a nucleus has migrated, can have no value as an argument for 

 the intercellular hypothesis of intercalated discs, since, aside 

 from their peripheral location, they could not as true intercellular 



