304 H. E. JORDAN AND J. B. BANKS 



Lhamon (17) and by King (15). It may represent a lymphoid 

 space, but we can find no evidence of lining epithelial-cells, in 

 which result we are in agreement with Lhamon and with King. 



The latter two investigators demonstrated the continuity of 

 the sheath and the enclosed lymphoid space' throughout the 

 entire bundle by means of injections with india-ink and Prussian 

 blue. Injection of silver-nitrate solution failed to reveal lining 

 cells. Lhamon (17) concludes that in hearts of beef, calf and 

 sheep the sheath does not simulate, except perhaps very re- 

 motely, a mucous bursa, as claimed by Curran; and that it is 

 not a part of the lymphatic system of the heart. 



The nuclei of the cells are located centrally, within a finely- 

 granular sarcoplasmic area free of myofibrils. The two nuclei 

 are almost invariably in very close apposition; frequently flat- 

 tened along the apposed, surfaces. They arise chiefly by ami- 

 totic division of a single nucleus of the original cell, a process 

 which can be observed in fetal hearts of from two to four months. 

 A few nuclei were observed in the segmented spireme condition 

 in the tw^o-month fetal heart, which would seem to indicate that 

 mitotic division also may occur in the earlier stages. In this 

 respect the bundle simply agrees with ordinary myocardium, 

 where nuclear division is originally mitotic and subsequently be- 

 comes exclusively amitotic. The tri- and quadri-nucleated condi- 

 tion of the bundle cells follows a later similar amitotic event. 



The myofibrils are relatively sparse, but are more closely 

 aggregated peripherally. They are collected in smaller irregu- 

 lar bundles, which peripherally are generally arranged parallel 

 with the borders of the cell. The telophragmata are conspicu- 

 ous among the bundles; between the bundles they appear more 

 delicate, distorted, and frequently interrupted. 



The serrations in the enveloping sarcolemma are fixation arti- 

 facts, due to the close union between telophragmata and sarco- 

 lemma and the unequal shrinkage in fixation between the myo- 

 fibril bundles and the sarcolemma. They are the homologues 

 of the sarcolemma festoons of the myocardium. The serrated 

 condition is rendered still more conspicuous in stained prepara- 

 tions by reason of the fact that the stain penetrates more pro- 



