306 Changes in the Muscle Cell of ^^ecturiis 



ach the chromatin spi'eads itself out on the inner surface of the nuclear 

 membrane and that this condensation is directly connected with the 

 formation of proz_ymogen. 



These and other facts lead to the conclusion that the position of the 

 nucleus, its greatly increased amount of chromatin and the lateral con- 

 densation of the latter are directly related to the formation of fibrillEe. 



D. Significance of Correlation of Cytoplasmic and ISTuclear 



Changes. 



If it be true that nuclear changes in the muscle cell are correlated 

 with phases of cytoplasmic activity, especially the formation of fibrillse, 

 we are naturally led to a further inquiry, namely : Does the nucleus of 

 the muscle cell, like that of the gland cell, build up and give off chrom- 

 atic material, which plays an important part in, if it does not direct, 

 cytoplasmic metabolism ? 



There are two structures in the muscle fil)ril which are basophilic in 

 staining reaction, viz., the anisotropic hand and the so-called Dobie's 

 line. 



Micro-chemical tests made by Macallum, 95, 219, and Eutherford, 97, 

 319, show that this band contains an iron and phosphorus-holding nuclein. 

 Macallum states that in the cells undergoing transformation into stri- 

 ated fibres, some of the chromatin dissolved in the cytoplasm (from 

 the yolk granules) finds its way into the nuclei, as in other cells gener- 

 ally, but the greater part appears to remain in the cytoplasm of the devel- 

 oping fibre, where it later passes into the dark band of the fibril. It is 

 especially noteworthy that ]\Iacallum regards this process as excep- 

 tional. In general, the chromatin derived from the yolk granules is 

 converted into nuclear chromatin. 



While I would in no way question the accuracy of ]\Iacallum's work, 

 I think his interpretation that the chromatin in tlie anisotropic or dark 

 band of the fibril is derived directly from the yolk instead of the nucleus 

 is a priori improbable. A serious, if not insurmountable, objection to 

 Macallum's view is the fact that in the regeneration of the adult muscle 

 cell the basophilic portions are differentiated in the entire absence of yolk 

 material. The supposition that chromatin is elaborated in the nuclei 

 for this purpose is confirmed by the fact that before the muscle cell 

 regenerates, the quantity of chromatin is greatly increased through re- 

 peated nuclear divisions in the injured end of the muscle cell. These 

 facts have led me to consider the nuclei as the source of the chromatin 

 found in the dark band and Dobie's line, that is, in the basophilic por- 



