VARIETY OF SENSATIONS. 341 



to distinguish certain tones, especially the various intermediate grada- 

 tions between two musical notes ; there are also persons, as we shall 

 hereafter explain, who are unable to appreciate certain colors, and are 

 hence named color-blind ; and instances of defective smell are likewise 

 met with. National peculiarities of sensation may account for the 

 love of certain colors, and for the special love of music, noticeable in 

 different peoples. 



Exaltations of sensation occur in the so-called mesmeric, somnam- 

 bulistic, or hypnotic states ; for in these the senses of temperature, 

 touch and hearing may be acutely manifested. 



It is not known whether such peculiarities and exaltations of sensa- 

 tion are owing to modifications in the recipient surface or organ, in 

 the internuncial nerves, or in the sensorial centres. Probably, in the 

 case of individual or national peculiarities, all these parts are modi- 

 fied ; but in the so-called mesmeric exaltation the change is perhaps 

 limited to the sensorial nervous centres. 



Suspensions of sensation may be produced in several ways : thus, 

 the topical application of cold, ether, chloroform, morphia, or other 

 anaesthetic agents to the sensory surface or organ, may suspend sen- 

 sation locally. Pressure, ligature, disease, or division of the inter- 

 nuncial nerve, may also interrupt or destroy sensation. Effusions of 

 blood, softening, or other morbid changes in the sensorial nervous 

 centre, are equally fatal to the sensory functions. Narcotics, taken 

 internally, or injected under the skin, and chloroform and ether in- 

 haled through the lungs, also suspend sensation by their general action. 

 There is one natural mode of suspension of the action of the senses, 

 which remains to be mentioned, and that is deep, the influence of 

 which is to be explained by its effects, not on the sensorial surface, or 

 the conducting nerve, but on the sensorial nervous centres or common 

 sensorium. It is said, that under the influence of sleep, sight, the 

 most acute sense, is the first to be suspended, then taste and smell, 

 next hearing, and lastly, touch. 



The memory cannot recall common sensations, nor, except rarely, 

 the sensations proper to the special senses ; but it can, the mental per- 

 ceptions produced as the result of these. 



The variety of sensations manifested by man, is very great, and the 

 ordinary subdivision of these, into common sensation, and five special 

 senses, viz., sight, hearing, smell, taste, and touch, by no means suffi- 

 ciently or scientifically expresses the whole range of our bodily sen- 

 sations. In such a classification, the sense of touch is recognized as 

 distinct and special, though more often regarded as a simple modifica- 

 tion of the common sensibility. Again, it neglects the distinctive 

 characters of certain other sensations, by including them under the 

 head of common sensation, especially the sense of temperature, i. e. t 

 of heat and cold, the muscular sense or the sense of internal effort 

 and resistance, the sensations of hunger, thirst, nausea, satiety, want 

 of breath, fatigue, and exhaustion ; and, lastly, the feelings which ac- 

 company certain mental states, such as imaginary sensations, and the 

 peculiar sensations experienced in deep emotions, whether pleasurable 

 or painful. From these so-called modifications of common sensibility, 



