TOUCH. 



1181 







illustrates the necessity for the transmission 

 of the vibrations along a solid medium. "The 

 valve of the door on which the percussion 

 is made by knocking, is a detached frame of 

 wood hung upon hinges, and the vibration is 

 therefore comparatively isolated and not pro- 

 pagated throughout the frame of the house, as 

 is the case when, in shutting the door, the 

 valve itself strikes the door-post, which is 

 identified with the framework of the build- 

 ing." In illustration of the acuteness of 

 this sense in his own person, Dr. Kitto states 

 that the lightest footfall upon the same floor 

 is quite sufficient to attract his attention, or 

 even to arouse him from sleep. " If any 

 small article," he continues, " such as a 

 thimble, a pencil, a penknife, or even a more 

 minute object, falls from the table to the 

 floor, I am often aware of it, even when 

 other persons sitting at the same table have 

 not been apprised of it by the ear. The 

 greater the number of my points of contact 

 with the floor, the stronger are the impres- 

 sions I receive : hence they are more vivid and 

 distinct when I sit than when I stand ; be- 

 cause, in the former case, not only my own 

 two legs, but the four legs of my chair, are 

 concerned in conveying the percussion to 

 my sensorium. And when the chair itself on 

 which I am seated has been subject to the 

 percussion, the sensation is such as baffles 

 description. For instance, a few days since, 

 when I was seated with the back of my 

 chair facing a chiffoniere, the door of this re- 

 ceptacle was opened by some one, and swung 

 back so as to touch my chair. The touch 

 could not but have been slight, but to me the 

 concussion was dreadful, and almost made me 

 scream with the surprise and pain, the sensa- 

 tion being very similar to that which a heavy 

 person feels on touching the ground, when he 

 has jumped from a higher place than he ought. 

 Even this concussion, to me so violent and 

 distressing, had not been noticed by any one 

 in the room but myself. * * * If these per- 

 ceptions are so acute in carpeted rooms, it 

 will be easily understood by how much more 

 intense they become upon a naked wooden 

 floor. The sensation then amounts to torture 

 as every movement or concussion, in any 

 part of the room, then comes with an in- 

 tensity of effect, far more than proportioned 

 to the difference in the impression which 

 would, under the same circumstances, be pro- 

 duced upon the auditory sense." 



It is interesting to remark that, notwith- 

 standing this acuteness of the sense in ques- 

 tion, it does not seem to convey (in Dr. K.'s 

 case at least) any information of the direction 

 or distance of the percussions, except such as 

 is afforded by their relative intensity. Thus 

 he says ; "I am unable to determine from 

 the information of the sensation itself, whether 

 it has occurred upon the floor above, or in 

 that below me, or in the passage or room ad- 

 joining that in which I may be at the time. 

 I am not aware that the impression is more 

 distinct from the floor above than from that 



below; but it certainly is more distinct in 

 another room of the same floor, than from 

 either the one above or below ; whence I am 

 much in the habit of referring to the next 

 room the percussions which make the strongest 

 impression on me. In this I am not seldom 

 mistaken. * * * The information is 

 equally defective, even in the very room I 

 may happen to occupy. If a book or other 

 object falls in any part of the room, the sen- 

 sation is painfully distinct, the percussion 

 being upon the very boards on which I stand ; 

 but even in this case, 1 am at a loss for the 

 quarter in which the circumstance has oc- 

 curred, and generally look for it in the wrong 

 direction, and have to scan the whole room 

 with my eye before I can make it out." It is 

 probable that the want of power to estimate 

 direction arises from the circumstance that 

 the communication of the percussions takes 

 place, in this and similar cases, through the 

 same channel (the floor) to the same parts of 

 the solid mass of the body, through which 

 the vibrations immediately spread in every 

 direction. It can easily be conceived that if 

 the percussions were transmitted through a 

 liquid medium, its vibrations, being propagated 

 in a more determinate direction, might affect 

 one or another part of the surface in such a 

 manner as to suggest the direction of their 

 source ; and that in this mode aquatic animals 

 endowed with a nervous apparatus at their 

 surface, specially adapted to be impressed by 

 such vibrations, might communicate with each 

 other through great distances. This appears 

 to be the case with regard to the Spermaceti 

 Whale, and probably others of the Cetacea. 

 It has been observed by the whale-fi.shers, 

 that when a straggler from a " school " is 

 attacked, even at a distance of several miles 

 from it, a number of its fellows bear down to 

 its assistance, in an almost incredibly short 

 space of time. It can scarcely be doubted 

 that this communication must be made through 

 the medium of the vibrations of the water, 

 excited by the struggles of the animal, or per- 

 haps by some peculiar instinctive movements 

 especially adapted for this purpose, and pro- 

 pagated through the liquid medium to the 

 large cutaneous surface of the distant whales. 

 And this idea is confirmed by the fact, that 

 the nerves which proceed to the surface of 

 the body pass through the layers of blubber 

 (which form the inner part of the true skin) 

 with scarcely any division, and then spread 

 out into a network of extreme minuteness as 

 soon as they approach the exterior of the in- 

 tegument. The expanse of such a network 

 over a thick layer of elastic tissue, whose 

 meshes are distended with oleaginous fluid, 

 obviously affords a condition peculiarly fa- 

 vourable to the reception of impressions ori- 

 ginating in percussion. 



After the details which have been given in 

 proof of the degree of exaltation of which the 

 general tactile sensibility is capable in the 

 human subject, we shall have less difficulty in 

 understanding that even the vibrations of air, 



