6i6.^ 307 



Cell-Physiology 



[The revised I'rincij/lcs of Biolugij wliicli I ;uii slowly [)iupaiiiiy i.s to contain additional 

 chapters ; sundry of thcni made needful by recent developments of biological science. 

 One of these, entitled "Cell-Life and Cell-Multiplication," describes, so far as brevity 

 allows, the revelations which late years have witnessed respecting the processes of cell- 

 division and cell-fertilization. Study of the facts and hypotheses, as set forth in recent 

 works, have suggested to me some interpretations which I have not met with. I have 

 thought it as well to publish them now : not waiting for completion of the first volume 

 of the Principles of Biuloiji) ; as this will be long delayed, even if ill-health does not pre- 

 vent completion of it. The following are the relevant passages. — Hkubkrt Spencek.] 



THE clieinieal composition of chromatin is highly complex, and 

 its complexity, apart from other traits, implies relative in- 

 stability. This is further implied by the special natures of its 

 components. Various analyses have shown that it consists of an 

 organic acid (which has been called nucleic acid) rich in phosphorus, 

 combined with an albuminous substance : probably a combination of 

 various proteids. And the evidence, as summarised by Wilson, 

 seems to show that where the proportion of pliosphorized acid is 

 high the activity of the sulistance is great, as in the heads of sper- 

 matozoa ; while, conversely, where the quantity of phosphorus is 

 relatively small, the substance approximates in character to the 

 cytoplasm. Now (like sulphur, present in the albuminoid base), 

 phosphorus is an element which, besides having several allotropic 

 forms, has a great affinity for oxygen ; and an organic compound 

 into which it enters, beyond the instability otherwise caused, has a 

 special instability caused by its presence. The tendency to undergo 

 change will therefore be great when the proportion of the plios- 

 phorized component is great. Hence the statement that " the 

 chemical differences between chromatin and cytoplasm, striking and 

 constant as they are, are differences of degree only ; " and the con- 

 clusion that the activity of the chromatin is specially associated with 

 the phosphorus. 



What, now, are the implications ? Molecular agitation results 

 from decomposition of each phosphorized molecule : shocks are con- 

 tinually propagated around. From the chromatin, units of which 

 are thus ever falling into stabler states, there are ever being diffused 

 waves of molecular motion, setting up molecular changes in the 

 cytoplasm. The chromatin stands towards the other contents of the 

 cell in the same relation that a nerve- element stands to any element 



