178 EXPERIMENTS OF HOME. 



Dr. B. It is owing to a deficiency of the rete mu- 

 cosum which contains the colouring substance, and it 

 sometimes occurs in the inferior animals. White speci- 

 mens have been found of the rabbit, ferret, mouse, wea- 

 sel, fox, bear, beaver, rhinoceros, camel, elephant, buf- 

 faloe ; the crow, black-bird, canary-bird, partridge, and 

 a great many more. 



Emily. And it is this peculiar appearance of the skin 

 when the rete mucosum is known to be absent, which 

 induces you to think that it may be present in the white 

 races, and be the seat of their various tints ? Well, the 

 argument seems to be sound, and for want of a better, I 

 will adopt your opinion for the present. 



I should like to know however, what the use of the 

 black rete mucosum can be to the Negroes ; or, if any 

 purpose be answered by it, which is not by the white 

 one of other people. 



Dr. B. Sir Everard Home has tried some experi- 

 ments, the result of which proves that the black colour 

 enables them to resist, in a remarkable degree, the ra- 

 diant heat of the sun's rays. 



Emily. Pray, what were these experiments ? Black 

 I always thought, absorbed heat, and of course, made 

 the body hotter over which it is placed. 



Dr. B. This is true of unorganized matter, but not 

 so it seems, when we speak of this colour in reference to 

 animal bodies. However, I will relate the experiments, 

 and you may judge for yourself. This gentleman, among 

 other experiments, exposed the backs of his two hands 

 to the sun's rays, with a thermometer upon each, one 

 hand being covered by a piece of black cloth under 

 which the back of the thermometer was placed, and the 

 other being freely exposed without any covering. The 

 result was, that though the thermometer under the cloth 

 stood four or five degrees higher, than the other, yet in 

 every one of these trials, the exposed hand was scorched, 

 while the other did not suffer in the slightest degree. 



At another time, when the thermometer in the sun 



