615 



serve as boimdries to divide the heart into definite cells. "Segmen- 

 tation'' and "fragmentation" can not, therefore, be distinguished as 

 conditions of rupture occurring in intercellular structures, and in the 

 ''cell-bodies"' respectively. Furthermore, our observations upon rup- 

 tured heart muscle show that the fractures, whether they correspond 

 nioi-phologically more nearly with the "segmented" type or the "frag- 

 mented'' type of earlier writers, always occur in relation to the inter- 

 calated discs. These discs occur anywhere in the muscle fibres -near 

 and over the nuclei as well as remote from them. And whatever the 

 nature of such processes may be, the pathological processes involved 

 in bringing about the ante-mortem rupture of cardiac fibres act upon 



Fig. 1. Fig. 2. Fig. 3. 



Fig. 1. Short portion of fibre of monkej^ heart showing super-nuclear position 

 of three discs. 



Fig. 2. Two granular discs of monkey heart at different levels of focus. In 

 passing from the higher to the lower level of focus no connecting membrane or 

 riser appears. 



Fig. 3. A two-step, comb-like disc of monkey heart. The two portions are 

 connected by a course deep-staning membrane. The "teeth" of the "comb" are 

 interpreted as locally contracted portions of adjacent fibrillae. 



the discs and, seemingly by weakening or degenerating them, lead to 

 a rupture of the fibres. 



It is interesting to note that in diseased heart muscle, the degree 

 and duration of the morbid condition is reflected in the character of 

 the intercalated discs. In the extreme phase of pathological alteration 

 in hypertrophy (e. g. heart described in article in Anat. Record, June 9th., 

 1912) all the discs are of the very irregular zigzag type. The lines 

 of fracture are of identical character, leaving no doubt as to the locus 

 of fragmentation. In hypertrophied hearts from cases of less prolonged 

 fatal illness (for an excellent specimen of this type, with full history, 

 we are indebted to Mr. K. B. Steele) only a majority of the discs are 

 of the zigzag type, and only relatively few are of extreme irregularity. 

 But again, fragmentation occurs along the lines of the discs. 



