LIFE AND ENERGY 39 



The result is that an excess of OH ions remains, giving an alkaline 

 reaction to the solution. 



The adsorption of the free base of " basic " dyes is connected 

 with the hydrolytic dissociation of these salts, since the base is 

 a weak one. Being insoluble in water, it forms a colloidal solution 

 therein, and, owing to its giving off OH ions, becomes electro- 

 positive and powerfully attracted by a negative surface. Most of 

 the " acidic " dyes are salts of fairly strong acids (sulphonic acids), 

 and are very little, if at all, hydrolysed in solution. 



The Nucleus of the Cell 



The presence of a special component in the more highly 

 developed cells has been mentioned. Most of the facts concerning 

 the nature of protoplasm, given in the preceding pages, apply also 

 to the nucleus, but it has functions peculiar to itself. As yet very 

 little can be said about how these are performed. We know that 

 if a cell, such as an amceba, is divided so that one part only retains 

 the nucleus, this part will continue to live, while the other part 

 will, sooner or later, die and disintegrate. 



When nucleated cells multiply by subdivision, the nucleus 

 usually undergoes a complicated process of activity, to which 

 further attention will be given in the last chapter. It has been 

 supposed, also, to be concerned with the formation of certain 

 structures which appear in the cell, but it has to be confessed that 

 we are still very much in the dark as to its mode of operation. 



Mitochondria 



The same statement of uncertainty must be made with respect 

 to those bodies or granules in the cell protoplasm, to which the 

 above name has been given. They have various shapes, and have 

 been seen in living cells, where they appear to undergo changes in 

 the course of the activity of the cell. They have a special attraction 

 or affinity of some kind for a particular group of dyes, known as 

 the derivatives of di-ethyl-safranin. 



The subject matter of the preceding chapter is undoubtedly a 

 difficult one, but a comprehension of it is necessary before we can 

 proceed further with profit. The student is recommended to refer 

 back to it from time to time as he meets with phenomena, which 

 require a knowlege of the particular facts referred to here if they 

 are to be understood. 



