TOUCH, PRESSURE, AND LOCATION 351 



that of a small and a large orchestra, when the intensity does not differ. 

 How all these differences are represented by the mechanisms of the ear 

 is quite unknown. 



The direction from which sounds come, biologically often of great 

 importance, is given the individual by his comparison of the respective 

 intensities of the sensation in the two ears. When these are equal it 

 is considered that the sound is originated either directly in front or 

 directly behind the middle of the head. 



THE PERCEPTION OF OBSTRUCTIONS. Another experience given us 

 by the ears is that of perceiving without aid from the eyes an obstruction, 

 such as a wall or even a book held broadside close by. There is in this 

 a feeling of being shut in. This sensation probably comes from inappre- 

 ciable sound reflected from the object into the ear or ears. It is expe- 

 rienceable, however, when no sounds are audible as such, and when all 

 air-currents are excluded. It probably corresponds to some special 

 adjustment of the apparatus in the middle ear (William James). 



TOUCH, PRESSURE, AND LOCATION. 



These senses are probably only aspects of but one^ sensory experience. 

 When the stimulus is of weak intensity and of short duration we perceive 

 ''touch," and when it is strong enough to bend the skin downward we 

 fell it as "pressure," but in every case there is inherent in the sensation, 

 we know not how, awareness also of the location on or in our bodies 

 of the stimulus (its "local sign"). In general, then, it will be understood 

 in what follows that the two last-mentioned aspects of the sensation are 

 always involved, although we may use only the term touch. Included also 

 in a list of the various afferent end-organs of this sense of location should 

 be included those of the joints and muscles in some cases perhaps, but 

 these have already been described under kinesthesia. 



Organs and Functions. At various times and by different observers 

 there have been described at least seven sorts of afferent nerve-endings 

 which probably are concerned with tactile sensibility. It is possible 

 that some of these are concerned with the temperature-senses, or with 

 pain, etc., but for this there is at present no direct evidence. The seven 

 or eight probable tactile end-organs are as follows : Meissner's corpuscles, 

 the spheric end-bulbs of Krause, the Vater-Pacinian corpuscles (includ- 

 ing the Golgi and Mazzoni and other variants), the elastic-tissue spindles 

 of Ruffini, the nerve-rings of Bonnet, and the tactile menisci. Two of 

 these, the cylindrical end-bulbs and the Vater-Pacinian corpuscles, are 

 found also in muscle and in tendon, and have been described already. 

 We find in these various organs none of the mechanical or chemical 

 intricacy so discouraging in trying to understand Corti's organ and the 

 retina, but we do find much uncertainty about their specific functions. 

 The presence of these afferent nerve-endings in so large a variety sug- 

 gests once more in a striking way the complexity of the means by which 



