1054 ON CUTANEOUS AND [BOOK in. 



case of the skin an excessive or violent stimulation is necessary 

 to produce this effect, whereas a nerve may be directly stimulated 

 by so slight a stimulus as to give rise to hardly more than dis- 

 comfort without distinct pressure or temperature sensations being 

 felt ; and we can hardly suppose that in such a case these are 

 present but are annulled by an amount of pain so slight as that 

 which is produced. Thus making every allowance for the sug- 

 gestion that sensations of pain may override and obscure con- 

 comitant sensations of touch and temperature, we seem driven 

 to the conclusion that the latter sensations can only be developed 

 by help of special terminal organs, and that a stimulation of the 

 nerve fibres themselves if it produces any effect at all on con- 

 sciousness gives rise to pain, and to pain alone. 



We are in this way led to conceive of the skin as provided 

 on the one hand with specific fibres ending in specific terminal 

 organs and serving for sensations of touch and temperature, 

 and on the other hand with fibres of common sensibility having 

 no such specific terminal organs, the two kinds of fibres being 

 mixed together in the common cutaneo-us nerve. These fibres 

 moreover have not only different peripheral but also different 

 central endings, and during at least some part of their course 

 run in different tracts or in a different manner in the central 

 nervous system ; for as we saw in treating of the central 

 nervous system ( 508) cases of disease of the central nervous 

 system have been recorded in which over certain cutaneous 

 areas sensations of touch had been lost, while common sensi- 

 bility and sensations of pain remained, or vice versa. We may 

 add that the difference between the central paths or endings of 

 the nerves of touch and those of pain is further shewn by the 

 fact that in certain nervous diseases (tabes) when the skin is 

 pricked with a pin, the contact of the pin may be felt as mere 

 touch for so long a time as one or two seconds before pain is felt ; 

 the diseased condition enormously delays the transmission of the 

 impulses of pain but has not so much effect on those of touch. 



655. We may go a step further; there is a certain amount 

 of evidence that the terminal organs and fibres concerned in 

 touch proper, in sensations of pressure, are different and separate 

 from those concerned in sensations of heat and cold. In the 

 first place the general topographical distribution over the sur- 

 face of the body of sensitiveness to pressure is different from 

 that of sensitiveness to temperature. A familiar instance of 

 this is seen in bringing the palm of the hand to touch the fore- 

 head. In the former the sense of touch is highly developed, in 

 the latter the sense of temperature ; hence with the forehead 

 we feel that the hand is warm or cold, with the hand we feel 

 that the forehead is rough or smooth ; at least these two feel- 

 ings respectively preponderate, the one in the one part, the other 

 in the other. In the second place, if the stimulation of the 



