8 INTRODUCTION 



complete lack of proof that the bodies isolated are in the same 

 condition as in the intact cells. 



It would, indeed, be very surprising if there were not many 

 and dramatic changes in the organisation and composition of 

 both nuclear and cytoplasmic bodies as the result of maceration 

 and addition of the various solutions which are used in fraction- 

 ation. The nucleus and the cytoplasm are both very complex 

 colloidal systems. Studies by Chambers and others on cell 

 nuclei have shown that when the nucleus is removed from the 

 cell by microdissection it commonly either sets into a gel or 

 dissolves: in either case a profound change occurs as soon as 

 the nucleus is removed from its normal environment. De Fon- 

 brune, and Lorch and Danielli have found that, although a 

 nucleus may readily be transferred from one cell to another 

 in a viable condition provided that it does not come into con- 

 tact with the environment of the cell, a few seconds' contact 

 with the environment is sufficient to destroy the viability of the 

 nucleus. Dr. Dounce has informed me that he has compared 

 the composition of nuclei isolated from macerated cells by cen- 

 trifugation in non-aqueous solvents with nuclei isolated by 

 centrifugation in aqueous solvents. The nuclei from the non- 

 aqueous solvents contain almost twice as much material as do 

 those from the aqueous solvents. From these few remarks it 

 is quite clear that one should anticipate profound changes in 

 the organisation of the nucleus when it is removed from its 

 normal environment, and that these changes must include dif- 

 fusion of substances out of the nucleus, and probably also dif- 

 fusion of substances into the nucleus. It should be the first 

 responsibility of the investigator to ascertain the extent to 

 which morphological changes and diffusion artefacts are in- 

 volved in these isolation techniques. It seems probable that at 

 the present time the only work of this type, i.e., on isolated 

 nuclei, which is reliable is that of Brachet and of Callan on 

 some of the properties of the whole nuclei of amphibian oocytes, 

 which were isolated by microdissection techniques. 



It is probable that the organisation of the cytoplasmic com- 

 ponents is just as labile as that of the nucleus, if not more so. 

 Often in relatively simple protein systems, such as blood 

 plasma, addition of foreign materials causes profound reor- 



