CH. L.] SLEEP AND NARCOSIS 747 



the early stages of Wallerian degeneration, the branch of the nerve- 

 cell which we call the axis-cylinder presents swellings or varicosi- 

 ties, produced by hydration or some similar chemical change. The 

 monilif orm enlargements seen during the temporary pseudo-degenera- 

 tive effects produced by anaesthetics are comparable to this. These 

 enlargements are therefore not the primary cause of loss of conscious- 

 ness, but are merely secondary results of changes in the cell-body. 

 When a tree begins to wither the earliest apparent change is noticed 

 in the branches most remote from the centre of nutrition, the root ; 

 as the changes in the centre of nutrition become more profound, the 

 larger branches become implicated, but the seat of the mischief is 

 not primarily in the branches. This illustration may serve to render 

 intelligible what is found in nerve-cells and their branches. 



Moore and Eoaf believe that the substance in the nerve-cells (as 

 well as the other cells of the body) which is affected by chloroform 

 is the protein. They have shown that unstable compounds of protein 

 and chloroform are obtainable ; hence the greater solubility of chloro- 

 form in blood than in water. They compare the chloroform-protein 

 compound to oxyhaemoglobin, for it undergoes dissociation in the 

 same sort of way. Just as oxyhaemoglobin parts with its oxygen to 

 the tissue-cells, so the chloroform parts company from the blood- 

 protein, and enters into combination with the cell-protein, limiting 

 its activity and producing quiescence or anaesthesia. When the 

 administration of the chloroform ceases, the tension of chloroform in 

 the blood is no longer maintained, so the combination between the 

 cell-protein and chloroform dissociates, and anaesthesia passes off. 



The theory which has met with most favour in relation to anaes- 

 thetics, however, is that known as the Meyer-Overton hypothesis; 

 this theory, which has received abundant confirmation by numerous 

 observers, points out that the cells are easily permeable to the vola- 

 tile anaesthetics owing to the presence of fat and lipoid material in 

 their plasmatic membrane (see p. 330). It can hardly now be 

 doubted that the solubility of the volatile anaesthetics in the lipoids 

 of the membrane (or, what comes to the same thing, the solubility of 

 the lipoids in the anaesthetic) is an important factor in anaesthesia ; 

 the anaesthetic thus enters the cell easily, and throws the lipoid con- 

 stituents of the protoplasm (and perhaps secondarily the protein 

 constituents also) out of gear, the net result being a lessening of the 

 oxidative changes which are essential in active vital processes. 



The volatile anaesthetics, and especially chloroform, are dangerous 

 drugs, and although their discovery is one of the greatest blessings 

 to suffering humanity, and in experiments on animals, means should 

 be adopted for preventing the fatalities which are even now too 

 frequent. It is specially needful that anaesthetists should not 

 administer the drug in a haphazard way, but take care that the amount 



