HABIT AND SYMPTOMS 57 



bacillus tuberculosis, typus humanus, may exist for months 

 in the body of the calf without losing its specific or typical 

 properties. 



But here, also, we see the action of another general law, 

 which I owe to my old teacher James Boss the neurologist, of 

 Manchester, the law namely that properties which have been 

 most recently acquired are those which are most easily lost, 

 with its corollary that the longer a given environment acts upon 

 the individual and the race, the more firmly fixed become the 

 properties acquired in consequence of that environment. Boss 

 used to point out that it is the muscles which distinguish anthro- 

 poids from other mammals — those of the thenar and hypothenar 

 eminences — which first atrophy in systemic nervous disease. 

 I have pointed out elsewhere 1 that this law is constantly in 

 evidence when we study cases of reversionary (phylogenetic 

 reversion) and familial degenerations. What are the limits 

 within which this law is effective I hope to touch upon later. 



Habit and Symptoms 



We see these laws in action in the highest animals. There 

 can be no more striking examples of the action of the Law of 

 Habit than the abundant observations upon the production of 

 " antibodies " by the system once the cells have been stimulated 

 to elaborate them. But, as I pointed out some years ago, 2 

 we encounter examples in all directions. We find that after 

 an acute inflammation, be it of the lungs or the sinuses of the 

 nose, we encounter cases in which the discharge continues weeks 

 and months after the causative agent has disappeared and the 

 discharges have become sterile. To us as physicians it is im- 

 portant to keep this in mind, for the recognition of this class of 

 cases materially aids prognosis : it has to be remembered that 

 not infrequently what is commonly regarded as symptomatic 

 of functional, not to say anatomical, disturbance may after all 

 be one or other manifestation of habit, and therefore wholly 

 curable, provided the habit can be interrupted. May it not be 

 that an agitation that is progressing to-day in the daily and 



1 Principles of Pathology, vol. i. 2nd ed. p. 177. 



■ See the address upon " Habit, Symptoms, and Disease," Chapter VIII. 

 of Part II. of this volume. 



