92 



the hide is soaked, may be very small, and yet 

 produce a considerable effect. The principle 

 thing to be observed in tanning- is, that it be done 

 slowly, week infusions only being used in the be* 

 ginning of the process. The more slowly the 

 process is conducted, the better the leather be- 

 comes ; whilst, by a hasty process, the outer part 

 of the hide is supersaturated with tanning matter, 

 and the avenues to the interior parts are closed ; 

 hence a hard, brittle, and thin leather is pro- 

 duced* 



The Rete Mucosum, or net of Malpighi, which 

 constitutes the secretory organ of the skin, and 

 in which its nerves and absorbents are dispersed, 

 has not been examined. We only know, that 

 its black colour, observable in the skin of negroes, 

 may be bleached for some days by the applica- 

 tion of oxy-muriatic acid. The texture of the 

 Epidermis is very peculiar : It is not dissolved 

 even by long boiling in water, but it is dissolved 

 both by caustic alkalies and acids, and, in most of 

 its chemical properties, resembles the hair and 

 the nails. The greasy substance, with which it 

 is covered, has not been examined on the human 

 skin ; but VAUQUELIN has made an experiment 

 on that, which adheres to the wool in sheep, ad 



