THE NEWTS STOMACH DURING DIGESTION 453 



I have therefore been able to supply the link in the chain that seems 

 to have been missing in the work of previous investigators, namely the ob- 

 servation above recorded of an absolute diminution of chromatin, occurring 

 as a resuit of the production of prozymogen. 



Chromatin contains nucleic acid and an albuminous substance, it is 

 very stable and acts as an acid to bodies less acid than itself; therefore it 

 stains with methyl blue. In order that this stable body may pass into the 

 cytoplasm it is necessary that it should be rendered soluble (there being no 

 évidence of its passage bodily out of the nucleus) ; in this process some of 

 the albumin is removed as effete mateiial that goes to form the nucleolus. 

 This albumin acts as a base in présence of bodies more acid than itself 

 and therefore exhibits marked affinity for the eosine. Being now useless in 

 the nucleus it is extruded into the protoplasm there to be disposed of. 

 The more acid part of the chromatin passes into the cytoplasm where it 

 remains in an invisible state unless the phosphorous and iron it contains 

 are unmasked and revealed by dyes as directed by Maccallum. When the 

 cell begins to take up material from the blood (sérum albumin, etc.) this 

 prozymogen quickly links on some albumin to become zymogen in the form 

 of granules, nucleo-albuminous in nature which is probably a still less stable 

 compound than the prozymogen ; it now reacts as a feeble base to eosine 

 and hense is stained redwith that dye. Itis also readily soluble when brought 

 into contact with a weak acid either in the cytoplasm or elsewhere. In 

 other words both chromatin and zymogen have the same nuclein radicle, 

 their différence in staining property and solubility depending on the amount 

 of albumin linked on to it. 



With regard to the question of repair of the nucleus it can only be 

 brought aboutby the passage into it of substances from the cytoplasm, which 

 probably unité with nucleic acid in the nuclear juice to form a material 

 analogous to chromatin, i. e. the blue staining lanthanin granules precipi- 

 tated by mercuric chloride. This material seems gradually to give up its nu- 

 cleic acid to increase the chromatin, leaving a less acid material in the juice 

 which, when precipitated with corrosive sublimate, stains lilac, a tint inter- 

 mediate between blue and red. Finally also this material seems to be 

 removed, possibly passing to .increase the size of the nucleolus and may or 

 may not be in sufficient quantity to induce some nucleolar expulsion during 

 the réparation stage. When this material is ail disposed of, the nuclear juice 

 when precipitated stains as in the resting cell, i. e. the nucleus has become 



57. 



