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H. E. JORDAN AND K. B STEELE 



adult heart, however, they are meager in amount. Whether 

 this fact is due exclusively to the young, or, in part also, to the 

 diseased condition (tubercular meningitis) is not at present clear. 

 In the case of guinea-pig it is certain that the discs are relatively 



20 



21 



Fig. 20 Cardiac muscle of guinea-pig of four weeks of post-natal life. The 

 intercalated discs appear aggregated in the axis of the mesh, are of simple charac- 

 ter and mostly of paler or darker granular composition. 



Fig. 21 From same preparation as fig. 20, showing the beginning of the for- 

 mation of step-like discs. 



less abundant and simpler in young than in the adults. Possibly 

 the same relation obtains throughout mammals. However, there 

 may also be a relationship between the discs and the condition of 

 health and disease, a point which is now being investigated. 



