190 president's address. 



more important part in their mental processes than in those of 

 man, partly on account of the greater simplicity of their mental 

 endowments, and partly on account of the disturbing action of 

 the will in man. By this law contiguous or similar sensations 

 or volitions or emotions have a tendency to cohere and mutually 

 to suggest each other without effort, and, as it were, instinc- 

 tively. Professor Bain has shown the physiological basis there 

 is for such law; and he has pointed out a circumstance in its 

 mode of operation which it is important to note when tracing the 

 action of the law in the lower animals. The cu-cumstance I refer 

 to is the influence of particular senses in modifying its action. 

 In man the visual nexus prevails. As is well known the sense 

 of sight takes the place of the other senses, and supplies the 

 form of nearly all our ideas and the links which bind them toge- 

 ther ; and it does so to the extent of colouring all our language 

 on the subject, and making it difficult for us to conceive trains 

 of thought under other conditions. Yet such conditions arise 

 from necessity, or the habitual use of some of the other senses. 

 The blind think in forms derived from touch. The musician 

 thinks in sounds ; the cook in tastes ; and these severally^have 

 their ideas associated more or less through these senses : and 

 who can doubt that the blind, but for intercourse with others 

 and the corrective effect of language, would manifest mental 

 habits which would be often obscure and perplexing. Now, 

 the predominance of the sense of smell in the dog, and its con- 

 nection with his natural instincts, no doubt exercise a similar 

 influence on the form of his ideas and the structure of his men- 

 tal habits. If we do not take this into account we shall often 

 mistake him and attribute perhaps to thought what is only an 

 instance of obscure association ; whereas, if we keep it in view, 

 it will help to throw light on several things that are difficult to 

 explain in his conduct — in the conduct of the sheep-dog, for 

 instance, and on that curious faculty the dog has of finding his 

 way in the absence of known or visible landmarks. 



I refer to this as indicating one source of obscurity in inter- 

 preting the actions of brutes. 



But there is another circumstance to be noted. The animals 



