On the Sense of Feeling. 295 



The bulb of a phaiierus is composed externally of a fibrous investing 

 membrane, to which its form is due j and which is perforated below for 

 the passage of the nerve aud vessels, and above for the exit of the hair. 



Within this membrane is a second, composed of the ramifications of the 

 blood vessels, and therefore highly vascular ; and within this is a third 

 membrane, composed of the interwoven filaments of the nerve. 



The interior of this bulb is filled by a pulpy cone, secreted by the 

 membranes enveloping it, and receiving a very copious supply of both 

 nerves and blood vessels. 



It is from the external surface of this cone, as well as from the internal 

 of the investing membrane, that the matter of the hair is deposited. 



The substance of each hair is, therefore, divisible into two parts : an 

 external, thin, hard, and polished, bestowed upon it by the vascular mem- 

 brane ; and an interna], softer, and thicker, which is formed upon the cone 

 which thus becomes the mould of the hair, which is in consequence 

 tubular. 



The thickness of hair varies considerably, and the colour enables us to 

 estimate the thickness. A German anatomist, with patience characteristic 

 of his nation, has left calculations on this subject : from these it appears 

 that in a square inch of scalp, there are contained, of black hairs, five hun- 

 dred and seventy-two ; of chesnut, six hundred and eight; and of light 

 coloured, seven hundred and ninety ; so that the diameter of a hair is least 

 in light hairs, and these are finer the lighter their shade. 



Hair is exceedingly durable, and is occasionally found uninjured in old 

 tombs, when the rest of the body has crumbled into dust. 



Appended to the cuticle, and falling ofi" with it after death, are the nails ; 

 they are thick and hard, but inorganic and laminated, growing rapidly 

 from the root to the extremity, and reproduced about every six months. 



Ceneath the skin which covers the fingers, and upon the back of the last 

 phalanx, are placed a series of bulbs, in very close apposition, the secre- 

 tions of which grow up together, and form the nail in man, the hoofs and 

 similar appendages in other animals. The general form of the nail de- 

 pends upon the surface on which it rests j the nails support the ends of the 

 fingers, resist pressure, and thus subserve the organ of touch. 



Having thus anticipated a little our order, to adopt the more complete 

 human integument as a type and standard, we shall drop at once to the 

 bottom of the scale, and trace the gradual development of the sense as we 

 approach the summit j and as this sense resides in the integument, we shall 

 consider the various forms, colours, and modification, of that structure, as 

 the investment of the animal frame, and the passive organ of tact; and 

 next point out those restricted portions of it which are more specially or- 

 ganised, and which, admitting of being placed in contact with more planes 

 than one of a foreign body, constitute the active organ, that of (ouch. 



The animals of infusions, upon whose organisation so much light has 



