32 THE EQUILIBRIUM OF COLLOID AND 



mixtures containing as high, or higher, amounts of oxygen as are 

 present in atmospheric air so as to avoid asphyxiation from de- 

 ficiency of oxygen, it is found that carbon-dioxide has directly 

 poisonous effects upon the bioplasm. Thus, with 12 to 15 per cent, 

 of carbon-dioxide and 20 to 25 per cent, of oxygen, it is found 

 that animals become somnolent, and, as above stated, that the 

 urine contains glucose, while with 20 to 25 per cent, of carbon- 

 dioxide, even in presence of excess of oxygen, death rapidly occurs. 



The same effects are seen upon isolated tissues. Thus Waller 

 has shown that the first effects of minimal traces of carbon-dioxide 

 is to increase the excitability of nerve, while larger doses diminish 

 excitability, and finally all excitability disappears. Similar results 

 are found in unicellular organisms and in ciliary movements. 



All these results point to varying degrees of union and corre- 

 sponding stability or instability of union between carbon-dioxide 

 and bioplasm. 



Exactly similar results are everywhere evident in the applica- 

 tion of various drugs in therapeutics, in the action of the toxins 

 of disease, and in the action of antiseptics. There is the same 

 stimulating action seen, followed by paralysing action as the con- 

 centration is increased and the union between bioplasm and drug 

 becomes more stable and complete. 



One of the most striking results here is the adaptation between 

 drug and different types of cell, due to molecular variations in 

 the structure of the two reacting bodies causing them to possess 

 higher affinities . and unite at lower concentrations. For this 

 reason one type of cell takes up a drug and robs the other cells 

 of it, lowering the pressure in these other cells and the plasma, 

 so that the particular type of cell becomes loaded up at a pressure 

 which scarcely causes any uptake in other cells. 



On such a basis it is easy to understand why all mercury salts 

 produce the same specific action in syphilis, the result being due 

 to the free mercury ion and not being affected by the anion of 

 the salt used except in so far as this quantitatively alters the 

 degree of ionisation, and hence the concentration of mercury ion. 

 Similarly, the ferric ion in all iron salts stimulates the production 

 of erythrocytes in anaemia. So too quinine, and the alkaloids 

 generally, furnish a basic ion affecting specific cells of the organism 

 in each case, or of pathogenic foreign organisms present in it, for 

 which at different stages they possess special affinities. 



