CRYSTALLOID IN LIVING CELLS 331 



the animal. Short of this limit, stoppage of the positive ventila- 

 tion has the effect of restoring the heart to regular rhythm. 



Passing in the opposite direction, and observing the effects of 

 increasing amounts of carbon dioxide, administered in artificial 

 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 effect 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 anesthetics and antiseptics. There 

 is the same stimulating action seen, followed by paralysing action 

 as the concentration 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 



