308 NATURAL SCIENCE [May 



of an organism which it excites ; an interpretation congruous with 

 the fact that the chromatin is as near to as, and indeed nearer than, 

 a nerve-ending to any minute structure which it stimulates.^ 



Several confirmatory facts may be named. During the intervals 

 between cell-fissions, when growth and the usual cell- activities are 

 being carried on, the chromatin is dispersed throughout the nucleus 

 into an irregular network : thus greatly increasing the surface of 

 contact between its substance and the substances in which it is 

 imbedded. As has been remarked, tliis wide distribution furthers 

 metabolism — a metabolism which in this case has, as we infer, the 

 function of generating, not special matters but special motions. 

 Moreover, just as the wave of disturbance a nerve carries produces 

 an effect which is determined, not by anything which is peculiar in 

 itself, but by the peculiar nature of the organ to which it is carried 

 — muscular, glandular or other ; so here, the waves diffused from 

 the chromatin do not determine the kinds of changes in the 

 cytoplasm, but simply excite it : its particular activities, whether 

 of movement, absorption, or structural excretion, being determined 

 by its constitution. And then, further, we observe a parallelism 

 between the metabolic changes in tlie two cases ; for, on the one 

 hand, " diminished staining capacity of the chromatin [implying a 

 decreased amount of phosphorus, which gives the staining capacity] 

 occurs during a period of intense constructive activity in the 

 cytoplasm ; " and, on the other hand, in high organisms having 

 nervous systems, the intensity of nervous action is measured by 

 the excretion of phosphates — by the using up of the phosphorus 

 contained in nerve-cells. 



For thus interpreting the respective functions of chromatin and 

 cytoplasm, yet a further reason may be given. One of the earliest 

 general steps in the evolution of the Mctazoa, is the differentiation 

 of parts which act from parts which make them act. The Hijdrozoa 

 show us this. In the hydroid stage there are no specialized con- 

 tractile organs : these are but incipient : individual ectoderm cells 

 have muscular processes. Nor is* there any " special aggregation of 

 nerve-cells." If any stimulating units exist they are scattered. 

 But in the Medusa-?,t^gQ nerve-matter is collected into a ring round 

 the edge of the umbrella. That is to say, in the undeveloped form 

 such motor action as occurs is not effected by a specialised part 



^ While the proof was in my hauds there was published in Science Progress an essay 

 by Dr T. G. Brodie on "The Phosphorus-containia^ Substances of the Cell." In this 

 essay it is pointed out that " nucleic acid is particularly characterised by its instability. 

 ... In the process of purification it is extremely liable to decompose, with the result 

 that it loses a considerable part of its phosphorus. In the second place it is most easily 

 split u]) in another manner in which it loses a considerable jiart of its nitrogen. . . . 

 To avoid the latter source of error he (Miescher) found that it was necessary to keep the 

 temperature of all solutions dowa to O^C. the whole time." These facts tend strongly to 

 verify the hypothesis that the nucleus is a source of perpetual molecular disturbance — 

 not a regulating centre but a stimulating centre. 



