EXCRETION 131 



but seldom removes the dermis. The epidermis is thick 

 over the palms of the han<jls and soles of the feet ; else- 

 where it is thin. Not often seeing the whole thickness of 

 the skin, we do not easily obtain an idea of its real thick- 

 ness. The skin constitutes about one-fifteenth of the 

 body's weight, and if tanned makes a moderately firm and 

 thick leather very much resembling the pigskin used for 

 covering footballs, striking bags, etc. 



Mouth of Sweat Duct 



Horny Epider- 

 mis 



Soft Layer 



Papilla 



Dermis 



\ M 

 Vein Artery 



,Fig. 50. Section of Epidermis, showing Papilla. (Highly magnified.) 



The Epidermis. The epidermis consists of many 

 layers of cells packed closely together. The deepest cells 

 may be compared to grapes with their cell walls plumply 



