44 THE ACTIVE FORCES OF LIVING ORGANISMS 



attacks of asthma, when the supply of oxygen is to 

 a great extent cut off, is of such a kind as to suggest 

 very rapid production and incomplete oxidation. 

 Whether this result is a direct or an indirect one 

 really matters little, for it is evident that both in the 

 gland and in the nerve-cell a diminution of oxidation 

 causes excessive activity or movement. Contractility, 

 moreover, is a property of protoplasm in general, and 

 there is the less reason to make an exception of 

 nervous matter since the axis cylinder of a nerve- 

 fibre resembles chemically in its general features 

 muscular tissue. Experiment also confirms the 

 view that the nerve-cell, if it behave as ordinary 

 protoplasm, contracts and expands in accordance 

 with the changes in its chemical environment, and 

 in this respect the following passage is of great 

 interest : 



' Eef erring again to Ehrlich's observation, we can 

 see that if anaesthetics and hypnotics cause contrac- 

 tion of the protoplasm in the cells of nervous centres, 

 they will thus lessen oxidation and tend to diminish 

 functional activity. Such a contraction might be 

 caused not only by alkaloids like morphine, but by a 

 mere change in the reaction of the cell or of the fluid 

 surrounding it. When free cells, such as amoebffi or 

 infusoria, are treated with very weak acid they con- 

 tract, and with weak alkali they swell up. It there- 

 fore seems probable that mere diminution of alkalinity 

 by the products of tissue-waste may tend to lessen 

 oxidation in the brain-cells by contracting the proto- 



