C I > 7 
Moreover, whatever this fuppofed black Humour 
may be, or in whatever it may be contained, it muft 
be opaque, and the Fibres or Veflels of the Epider- 
mis muft be tranfparent, to fhevv this Colour thro’ 
them ; as we have (hewn, that the Skins of Negroes, 
but not of Whites, are opaque (Prop, I. II ) : But it is 
very probable, that none of the fubcutaneous Juices 
arc opaque, they being the ultimate Secretions of the 
fubtilcft Fluids of our Bodies, which, inftead of being 
opaque and black, muft rather become pellucid and 
white 5 Etcnim Corpora omnium opacifjlma, fi Eartes 
ipforum in fummam ufque tenuitatem commmuayitur , 
evadunt continuo plane perfeCleque pellucida ( a ). 
And the Skins of Negroes, being more callous or 
cartilaginous, muft contain rather fubtiler, and 
more pellucid aqueous Juices, than thofe of white 
People. 
Furthermore, if there was any fuch Thing as a 
black Humour in the Skins of Negroes, no doubt 
but it might be drawn out by fome means or other; 
but, altho’ 1 have macerated the Skins of Negroes, 
and particularly the Epidermis-, in warm Water, which 
readily diftblves the Juices of the Body, yet I never 
could extract any black Juices from them, by any 
fuch Maceration, or even by a more powerful Ex- 
preftion no more than Mr. Littre (as is related) 
could do, by more powerful Diffoivcnts. Nothing 
feems more likely to extrad this fuppofed black 
Juice, than the Adion of Fire, or Cantharides-, upon 
the VelTels which contain it, which abrade and tear (*) 
(*) Newton 0/>r. lib. II. Parc 3. Prop. IV^ 
the 
