60 PHILOSOPHICAL TRANSACTIONS. [aNNO 1744. 



that for a considerable length of time. Nevertheless she had continued to exist, 

 and had been capable of going about, begging from door to door. 



A parallel case of a scirrhous cerebellum is recorded in the Memoirs of the 

 Parisian Academy of Sciences for 1705. 



An Essay on the Causes of the different Colours of People in different Climates. 

 By John Mitchell, M. D. N°474, p. 102. 



The cause of the colour of negroes being a subject so little known, but so 

 much inquired after, and so curious and useful, as to excite the particular atten- 

 tion and inquiries of the learned in Europe, particularly the Academy of Bour- 

 deaux, in their prize-problems. Dr. M. therefore offered his thoughts on that 

 subject, having had frequent opportunities to make the proper and necessary ob- 

 servations. This problem supposes the knowledge of the causes of colours in 

 general ; so that if he can deduce the colour of the skin from its structure, &c. in 

 the same manner, and for the same reasons, from which the great Newton de- 

 duces the colours of other substances, it is all he pretends to, which will be as 

 much as that branch of philosophy will permit: and as this problem will include 

 the cause of the colour of the skin in general, he first inquires into the cause of 

 the colour of white people ; with a change from that colour in some preternatural 

 affections, whose causes seem not well understood. 



Prop. 1. — The Colour of white People proceeds from the Colour which the 

 Epidermis transmits; that is, from the Colour of the Parts under the Epidermis, 

 rather than from any Colour of its own. — The truth of this proposition will 

 plainly appear to those who consider, that the colour of white people is always 

 more or less clear or vivid, as the skin is thinner or thicker, finer or coarser; that 

 is, as it is more or less adapted to transmit the colour of the white parts below it. 

 These parts are the parenchyma of the skin, corpus reticulare, papillae nervosae, 

 the limpid and clear juices contained in the vessels, and perhaps the inner epi- 

 dermis itself may appear through its outer porous coverlet ; all which parts we 

 know are white, and are what appear so in white people. 



But this will be better confirmed, from the following considerations : 1 . The 

 palms of the hands, lips, &c. where the epidermis and skin are so thin as to 

 transmit the colour from any thing below them, appear red, or of the colour of 

 the red blood under them ; especially in those in whom the skin is fine and thin ; 

 but where the skin is thick and coarse, those parts appear almost of the same 

 colour with the rest of the body. 2. The blushings of the cheeks, and their 

 redness in fevers, seem to be another proof of this cause of their colour ; for, in a 

 moment, they change from a pale to a deep red; but no one will imagine, 

 that the epidermis then changes its colour, or power of reflecting the rays of 

 light ; but that it transmits the colour of the blood; which at such times i^ more 



