94 Mr, Mayo on Human Physiology. 



instance the lymphatic system, not the vascular system, be- 

 comes irritated, as if affected by transmitting an acrid sub- 

 stance. 



When, as life advances, the substance of the lungs be- 

 comes mottled with black matter, the bronchial lymphatic 

 glands put on a similar appearance : at the same time the 

 lymphatics in other parts do not change their colour ; and 

 the vessels, which pass through the blackened bronchial 

 glands, are not the bronchial veins, but the lymphatics from 

 the lungs. 



In examining the functions of the nervous system, Mr. 

 Mayo proposes as a subject for preliminary inquiry, What 

 are the moral phenomena common to human beings with the 

 lowest animals ? 



*' We attribute consciousness to animals from the resem- 

 blance of their habits to our own. We form definite ideas 

 respecting the nature and extent of their moral properties, 

 by explaining their habits upon the simplest principles, 

 which produce the like in us. 



'' The perception of a sensation is one of the simplest 

 affections of consciousness that we can conceive. Upon 

 analyzing this phenomenon, we distinguish three elements 

 contained in it : a material impression is communicated to 

 an organ sense, a change ensues in the physical condition of 

 the nervous system, and perception follows. Thus, in vision, 

 rays of light impinge upon the retina, an affection of the optic 

 nerve and brain ensues, and we see light or colour. Of the 

 three parts into which this phenomenon resolves itself, the 

 last alone is an affection of consciousness ; the two first are 

 affections of matter, the antecedence of which distinguishes 

 perception from mental phenomena, that resemble it. The 

 conception or imagination of objects in a dream is as vivid 

 and persuasive of their reality as actual perception, but is 

 not like the latter produced by impressions upon our organs 

 of sense. 



** The term sensation is legitimately used in two senses; 

 either to denote the physical change in our organs which 

 precedes perception, or as synonymous with the term per- 

 ception. By blending these two ideas, sensation is fre- 

 quently understood to signify an affection of the mind 

 resulting from material impressions, which is supposed to 

 be the proper object of perception ; but the element thus 

 assumed is a logical fiction. 



*' We can imagine a corporeal being, the moral properties 

 of which should be limited to sensation only ; it is possible, 



