334 THE SKIN OR ORGAN OF TOUCH. 



cribriform plate of the sethmoid bone, enveloped by fibrous 

 sheaths, and are distributed mostly upon the superior part 

 of the pituitary membrane, forming plexuses in its sub- 

 stance. The branches of the olfactory are seldom found to 

 pass lower than the middle spongy bone and the middle 

 part of the septum. "Thus," as Cruveilhier remarks, "while 

 the upper and extremely narrow part of each nasal fossa 

 is the essential seat of the sense of smell, the lower and 

 much wider part only gives passage to the air during the 

 act of respiration." 



Besides the special sense of smell, there is also the gen- 

 eral sense of feeling derived from the first and second divis- 

 ions of the fifth pair, or branches from the ophthalmic and 

 superior maxillary nerves, which are likewise distributed to 

 every part of the nose. These branches from the fifth, differ 

 from the olfactory in not having the plexiform arrangement. 



SECTION V. 



THE SKIN OR ORGAN OF TOUCH, (Fig. 19.) 



The sense of touch is coextensive with the whole external 

 cutaneous surface, and those portions of the internal cutane- 

 ous or mucous, which are adjacent to the skin and continu- 

 ous with it. The diffusive character of the sense of touch, 

 and the extent of the apparatus composing it, distinguish 

 it from the rest of the senses, whose limits are circum- 

 scribed and confined solely to the head and face. Though 

 it be true that the sense of touch resides generally in the 

 skin, yet it is also true that there are some portions in 

 which it is much more highly developed, ^,nd where the 

 sense of touch is said most especially to reside that is in 

 the skin covering the extremities of the fingers and toes 

 and here it is discriminated by the name of tact. 



The sense of touch enables every one to recognise the 

 pressure and presence of external bodies, when they come 

 in contact with his skin, also to determine many of their 

 physical properties, as form, size, weight, consistence and 

 temperature. But for the discernment of other qualities of 



