52 STRUCTURE OF THE CUTICLE. 



it is supposed by many to be merely an exudation 

 of albuminous mucus ; and although depressions are 

 obvious on its surface, and exhalation and absorp- 

 tion are proved to be carried on through its sub- 

 stance, it is still in dispute whether it be actually 

 porous or not. Probability is in favour of the affirm- 

 ative, and the circumstance of the pores not being 

 visible is no proof to the contrary, for the cuticle is 

 .so elastic that it may be perforated by a needle, 

 and yet the hole not be discernible even under the 

 microscope. The question is, however, one of little 

 moment, provided it be remembered that its texture, 

 whether perforated or not, is such as to admit of ex- 

 halation and absorption taking place through its sub- 

 stance. 



The structure of the cuticle is in admirable har- 

 mony with its uses. Placed as an insensible inter- 

 medium between external objects and the delicate 

 nervous expansion on the surface of the subjacent 

 true skin, it serves as a physical defence against 

 friction ; and while, by impeding evaporation, it 

 preserves the true skin in that soft and moist state 

 which is essential to its utility, it also, by impeding 

 absorption, enables man to expose himself without 

 injury to the action of numerous agents, which, but 

 for its protection, would immediately be absorbed, 

 and cause the speedy destruction of health and life. 

 This is remarkably exemplified in several trades, 

 where the workman is unavoidably exposed to an 

 atmosphere loaded with metallic and poisonous 

 vapours, or obliged to handle poisonous substances , 

 and where, without the obstruction of the cuticle, 

 the evil to which he is subjected would be aggra- 

 vated a hundred fold. Being destitute of nerves, 

 the cuticle is not hurt by the direct contact of ex- 

 ternal bodies, and being very thin, it blunts without 

 impairing the distinctness of the impression made 

 on the nerves of sensation. The necessity of this 

 latter provision becomes verv "bvious when the 



