176 TRANSACTIONS AND PKOCEEDINGS OF THE [Sess. LX\7. 



action takes place. The nervous system, in common with 

 other tissues, shows us many cases of insusceptibility, 

 e.g. to drugs and poisons. Tlie idiosyncrasy of one man 

 to a given drug in that he is peculiarly insusceptible to it, 

 is as well expressed by saying that, owing to the magnitude 

 of the functional inertia of some tissue of his, the drug 

 has no inliuence, while owing to the smallness of the 

 inertia of the tissues of another man, the drug has con- 

 siderable influence. The man whose cerebral protoplasm 

 has much anabolic functional inertia, e.g. with respect to 

 chloroform, will take a longer time to become anaesthetised 

 by that drug than some other man whose protoplasm has 

 less. 



III. In the more characteristically psychic sphere, 

 examples of functional inertia, psychic inertia, are 

 numerous, A person appears taller than he otherwise 

 does, if his clothing shows longitudinal striping — the idea 

 of extension up and down occupies the mind, and we carry 

 more of it over into the estimate of the person's height 

 than we would have done had he been differently dressed — 

 by its inertia (active phase) a given idea imparts to the 

 subsequent one some of the characters of itself. 



A 



B 



So in connection with the illusion as to the relative 

 lengths of the lines A and B — the lines are of equal 

 length, but B appears greater than A. Mental functional 

 inertia seems to be responsible for the erroneous estimate. 

 Owing to the manner in which the short converging lines 

 turn back, as it were, upon the line A, they suggest the 

 ideas of " backwards," " the end reached," " limited," and 



