148 THE CELL 



function normally. The nucleus is, therefore, necessary for life. 

 Ultramicroscopic examination shows that the grey mass is a 

 hydrophilic colloid (emulsoid). Chemical analysis of dead amoebae 

 confirms the ultramicroscopic examination. Water to the extent 

 of about 75 per cent, is dispersed in the colloidal complex and acts 

 as a solvent for certain crystalloids. The colloid is an aggregate 

 containing protein, fat and carbohydrate. The crystalloids are 

 to some extent adsorbed on the surfaces of the colloidal mass and 

 to some extent are in free solution. Hofmeister estimated that a 

 typical cell contains : 



225 X 10^^ molecules of water 



53 X 1012 molecules of protein 



166 X 10^2 molecules of lipide 



29 X 10^* crystalloid al molecules. 



The elementary chemical composition conveys little information 

 as to the properties of the complex. To say that protoplasm 

 contains a certain percentage of carbon, hydrogen, oxygen, nitro- 

 gen, sulphur and phosphorus in a colloidal state, and potassium, 

 calcium, sodium, chlorine and phosphorus in solution is not of much 

 use as a contribution to the study of life. It is just as preposterous 

 to appraise the value of great pictures in terms of the chemical 

 composition of the paints and pigments employed as to attach 

 any great significance to the chemical elements of a dead cell. 

 What is of great importance is the physical state of the matter, 

 just as the value of a painting lies in the physical juxtaposition 

 of pigments, an artistic blending of colour, light and shade, 

 v/hereby the eye is pleased, so the life of a cell depends on the size, 

 consistency, etc., of the colloid-crystalloid complex forming its 

 protoplasm. 



The water content of protoplasm is amazing in quantity and in 

 physical state. We have seen (Chap. YIII.) that certain colloids 

 have the property of imbibing large quantities of water and of 

 holding that water under considerable compression (see also 

 Experiment 39, Part II.). The physical properties of such 

 water differ markedly from those of free water. For example, its 

 vapour pressure will drop to a very low value and its removal 

 from the colloid will be very difficult. 



So, too, as has been pointed out in Chapter XL, is the fat 

 content of the cell imique. Every cell has a fairly constant 

 content of lipide, although when stained by the usual methods to 

 demonstrate fat, no evidence is given of such a content. This 

 masked fat is only made visible when the cell is diseased or disin- 

 tegrated. The process of phanerosis or the unmasking of fat may 



