340 CE/.L-C/IEA/fSTKY .LV/) CEl.I.-PUVSIOI.OGY 



If these facts arc considered in the lii;lU of the known staining- 

 reaction ot the nuclein series, we must admit that the following con- 

 clusions are something more than mere possihilities. We may infer 

 that the original chromosomes contain a high percentage of nucleinic 

 acid ; that their growth and loss of staining-power is due to a combi- 

 nation with, a large amount of albuminous substance to form a 

 lower member of the nuclein series, probably a nucleo-proteid ; that 

 their final diminution in size and resumption of staining-power is 

 caused by a giving up of the albumin constituent, restoring the 

 nuclein to its original state as a preparation for division. The growth 

 and diminished staining-capacity of the chromatin occurs during a 

 period of intense constructive activity in the cytoplasm ; its diminu- 

 tion in bulk and resumption of staining-capacity coincides with the 

 cessation of this activity. This result is in harmony w^ith the obser- 

 vations of Schwarz and Zacharias on growing plant-cells, the per- 

 centage of nuclein in the nuclei of embryonic cells (meristem) being 

 at first relatively large and diminishing as the cells increase in size. 

 It agrees further with the fact that of all forms of nuclei those of the 

 spermatozoa, in which growth is suspended, are richest in nucleinic 

 acid, and in this respect stand at the opposite extreme from the nuclei 

 of the rapidly growing egg-cell. 



Accurately determined facts in this direction are still too scanty to 

 admit of a safe generalization. They are, however, enough to indi- 

 cate the probability that chromatin passes through a certain cycle 

 in the life of the cell, the percentage of albumin or of albumin-radicals 

 increasing during the vegetative activity of the nucleus, decreasing in 

 its reproductive phase. In other words, a combination of albumin 

 with nuclein or nucleinic acid is an accompaniment of constructive 

 metabolism. As the cell prepares for division, the combination is 

 dissolved and the nuclein-radicle or nucleinic acid is handed on by 

 division to the daughter-cells. A tempting hypothesis, suggested ' 

 by Mathews on the basis of Kossel's work, is that nuclein, or one of 

 its constituent molecular groups, may in a chemical sense be regarded 

 as the formative centre of the cell which is directly involved in the 

 process by which food-matters are built up into the cell-substance. 

 Could this be established, we should have not only a clear light on. 

 the changes of staining-reactions during the cycle of cell-life, but also 

 a clue to the nuclear " control "' of the cell through the process of 

 synthetic metabolism. This hypothesis fits well with the conclusions 

 of other physiological chemists that the nucleus is especially con- 

 cerned in synthetic metabolism. Kossel concludes that the formation 

 of new organic matter is dependent on the nucleus,^ and that nuclein 

 in some manner plays a leading role in this process ; and he makes 



1 Schiefferdecker and Kossel, Gewebelehre, ji. 57. 



