34 STRUCTURE AND USES OF THE MUCOUS COAT. 



nor nerves, and may be cut or bruised without pain. 

 \yhen the hand or foot is macerated in water, the 

 nails and the cuticle show their identity of organ- 

 ization, by separating together from the dermis or 

 true skin below. The nails, like the cuticle, serve 

 chiefly to protect the subjacent parts from injury ; 

 and, accordingly, in those lower animals whose 

 manner of life subjects their feet to continual pres- 

 sure, and requires no nice exercise of touch, Nature 

 has provided horny and resisting hoofs for their pro 

 tection, instead of a merely thickened epidermis. 



To produce thickening of the cuticle, exercise 

 must be gradual, and not too severe. If, for ex- 

 ample, a person takes a very long walk, rows a boat, 

 or makes use of a heavy hammer for a few hours, 

 without having been accustomed to such an effort, 

 there is no time for the cuticle to thicken, and de- 

 fend itself from the unusual friction. The parts 

 below, being inadequately protected, become irri- 

 tated and inflamed, and throw out a quantity of 

 watery fluid or serum on their surface, which raises 

 up the cuticle in blisters, and by making it painful 

 to continue the pressure, obliges the person to de- 

 sist from an exercise which, if continued, would 

 evidently soon alter the structure of the sentient 

 nervous filaments, and for ever unfit them for theii 

 proper uses : so that even in this result beneficence 

 and wisdom are prominently displayed. 



Immediately beneath the scarf-skin, and between 

 it and the true skin, is the mucous coat, rete mucosum, 

 or mucous network, which is remarkable chiefly as 

 being the seat of the colouring matter of the skin. 

 It is seen with difficulty on dissection except in 

 Negroes, in whom it is thick. It is exceedingly 

 attenuated in albinos, and is in fact thick in propor- 

 tion to the depth of colour. It is destitute of blood- 

 vessels and nerves, but, like the epidermis, is per- 

 meable by other bodies. The colouring matter is 

 said to be the same as that of the blood ; Davy and 

 Blumenbach, however, regard it as carbon. 



