NUCLEI OP ANIMAL AND VEGETABLE CELLS. 



133 



? 



The first contraction of the nucleus is called by Auerbach 

 water-shrinking } while the subsequent tumescence of nucleoli 

 is styled an internal swelling of the nucleus. 



Solutions of salts and of acetic acid act upon nuclei 

 in a manner which varies according to their percentage 

 strength. For example, so-called indifferent solutions of Na CI 

 (•5 — 1 per cent.) produce a greater distinctness of nucleoli, 

 intermediary granules and nuclear wall, which is in reality 

 a hardening of the nucleus. Solutions which are more 

 dilute produce a shrinking like that above described ; below 

 this, again, shrinking gives place to internal swelling as the 

 characteristic alteration (Plate XI, fig. 2 B) ; while solutions 

 containing very little salt indeed produce the final result of 

 the action of water, viz. the general swelling of the nucleus. 

 Above the point of indifference the action of solutions 

 resembles that of solutions below it, the stronger solutions 

 producing an internal swelling of the nucleus like the 

 weaker solutions ; while the strongest solutions have an 

 action like that of the indifferent strengths themselves 

 (Plate XI, fig. 1, h, i, k). These facts suggested a method 

 of classification of the various strengths of solution which 

 is illustrated in the following table '? 



Upper region of hard- 

 ening 



Upper region of 

 ternal swelling 



in- 



Lower region of hard- 



NaCl. 



35 p. c, 

 14 



C14 

 1 1-5 



C 1-5 

 X 0-08 



Lower region 01 in- \ q., 

 temal swelling 1 q.. 



0-08 

 008 

 001 



Region of 

 swelling 



general 



0-001 

 0-000 



7 Shrinking ■ 

 3 ofnucleus. 



Swelling 



of 

 nucleoli. 



Sugar in all solutions, from the weakest to those which 

 contain 60 per cent., causes the nuclei to swell up; and 



' Cf. Heat-rigor. 



' In this table the figures represent the percentage strengths of the 

 solutions used. The whole range of strengths is divided into regions, each 

 characterised by a mode of action upon nuclei. Thus, of solutions of 

 common salt, all those whose percentage strength ranges from 35 per cent. 

 to 14 per cent, exert that action on nuclei which is termed hardening. 



