158 INTRINSIC ACTIVITY OF SECRETING CELLS 



We see, therefore, that a high solubility of any dissolved sub- 

 stance in a supposed lipoid membrane or in the cell protoplasm, 

 will cause a corresponding accumulation of that substance in 

 the lipoid membrane or in the cell protoplasm, but cannot act 

 as an engine or energy producer for sending the substance through 

 the cell as a secretion or an absorbed product. 



The substance taken up as a result of higher solubility, such 

 as an anaesthetic absorbed by lipoids, or by fat in ordinary adipose 

 tissue, is hence imprisoned to that same extent in the fat or lipoid, 

 and kept from attacking or combining with the protoplasm ; and 

 accordingly the presence of such bodies, instead of aiding or causing 

 anaesthesia, act in the opposite sense by forming a reservoir for 

 the anaesthetic where it is inert so far as the cell protoplasm is 

 concerned, which is its real objective so far as production of 

 anaesthesia is concerned. 



The view expressed above, that those substances which are 

 actively absorbed and retained by the tissue cells form unstable 

 physical or chemical compounds with the cell protoplasm dependent 

 upon the osmotic pressure of such substances, cannot any more than 

 the others which have been criticised be put forward as an explana- 

 tion of the active work of the cell in secretion and absorption, 

 when the product is not to be retained in the cell, but is to be turned 

 out in greater concentration than that at which it entered. For 

 substances in such unstable combination, although subject to 

 different laws of relationship between concentration and osmotic 

 pressure, obviously come into equilibrium also at a given point 

 of concentration and osmotic pressure, and hence their formation 

 cannot be turned into a continuous source of energy for the per- 

 formance of work by the cell, such as is required to fit the case of 

 secretion. 



The formation of such unstable compounds is capable of 

 explaining the selective uptake and retention of constituents 

 by the cell, just as the different solubilities of different constituents 

 by the cell protoplasm or lipoids may explain such uptake or 

 retention, but neither view can explain more than this. Before 

 passing on to a consideration of the energy changes involved in 

 secretion, and the possible explanation of such changes, it may 

 be well, however, to point out that the view of formation of unstable 

 chemical combinations between cell protoplasm and selectively 

 absorbed and retained constituents, fits the observed facts much 



