4 Chapter III. 



which Haacke observed in the Makis, and classifies as 

 mental generalizations, to a critical analysis. 



On account of the pleasant irritation of the nerves 

 produced by the tobacco-smoke which Mr. Haacke re- 

 peatedly blew at them, the Makis regularly felt the 

 necessity of scratching themselves. The constant con- 

 nection of the olfactory perception of the smoke with a 

 feeling of itching and the consequent impulse to scratch 

 themselves, was apparently due to instinct, to the in- 

 herited disposition of their sensitive cognition and ap- 

 petite. But the olfactory perception of the smoke was 

 not less regularly preceded by the sight perception of 

 some one approaching and emitting smoke towards their 

 nostrils, and by the subsequent perception of the sense 

 of feeling. In consequence of its frequent repetition 

 this double impression of the sight and of feeling be- 

 came so intimately connected with the subsequent pro- 

 cesses that all of them finally formed one constant 

 process of association, which spontaneously led from the 

 first link in the chain of psychic activity to the last, even 

 when several intermediate links were missing. The 

 interior sensile imagination supplied the missing links 

 which were originally an experience of the outer senses, 

 and replaced these exterior perceptions by images of the 

 sensitive memory. This is the only natural explanation 

 of the fact that the Makis at last stretched forth their 

 heads and prepared for the subsequent operation of 

 scratching, when persons only pretended to blow at 

 them, and that they were induced to scratch themselves 

 merely by a perception of feeling, even without the 

 olfactory perception of the smoke. 



This whole psychic process consists solely of sense 



