IV. An Effay upon the Caufes of the different 
Colours of People in different Climates \ hy 
John Mitchell, M. D. Co?nmunicated to the 
Royal Society hy Mr . Peter Collinfon, 
E R . & * 
PE at f e y e - HE Caufe of the Colour of 
ml Meetings, from Mt VT , ^ . . 
May 3 . to June 14. §j Negroes being a Subjed fo lit- 
1744- JL r ^ e known, but fo much in- 
quired after, and withal fo curi- 
ous and ufeful, as to excite the particular Attention 
and 
* Extract of Fart of Dr. Mitchell’s Letter to P. Collinfon, 
F. R. S. from Urbana in Virginia, April 12. 1743. 
sir , 
T Promifed you Pome Returns for your Favours, by fending you my 
Effay on that Arrange Phanbmesion in Nature, the Caufe of the 
Colour of Negroes. 
I cannot promife you much, becaufe my daily Employments engrofs 
fo much of my Time: But this I Avail beg Leave to fay, that with 
great Care I have made the Experiments and Obfervations on purpofe 
to find out the Truth. I muft own I was furprifed at firft to fee 
them differ from the Opinions of fome learned Men ; efpecially in 
Matter of Fad, which they rather allege than prove, relating to the 
fluid Mucus of the Cuticula , or Corpus reticulare ; for which Reafon 
I repeated my Experiments on living Subjeds feveral times, but could 
never fee any Tokens of that black Juice. 
I am apt to think, that the Anatomifts, perceiving the Corpus reti- 
culare in dead Bodies to be a fofc pappy Subftance, have rather imagin’d 
than really found it to be, or contain, a fluid mucous Humour. 
But, as I am afraid this Will come too late for a Solution of the 
Prize-Problem, propofed by the Academy of Bourdeaux. If you 
think it deferves fo great an Honour, pray communicate it to the 
Royal Society , and if it merits their particular Regard, I fubmititto 
be printed in your learned and curious Memoirs, i am 
Tour obliged humble Servant , 
John .Mitchell. 
