g6 THE MICROSCOPE. 



about twenty-two years of age, however, dark copper- 

 coloured or brown spots began to appear on the face 

 and hands, but these have remained limited to the 

 portions of the surface exposed to light. About the 

 time that the black colour of the skin began to dis- 

 appear, he completely lost his sense of smell ; and 

 since he has become white, he has had measles and 

 hooping-cough a second time." This occurred in 

 1852. A case of partial disappearance of the black 

 colour of the negro's skin was brought by Dr. Inman 

 before the Zoological section of the British Association 

 at Liverpool in 1854.* 



You notice the perspiratory glands and ducts figured 

 in the engraving at c and g. By means of these organs 

 a transpiration of fluid holding excrementitious matters 

 in solution takes place. -The glands consist of a 

 number of long convoluted tubes, at first dividing into 

 two branches, and then re-uniting into a single tube or 

 duct opening at the surface of the epidermis. The 

 number of these perspiratory pores is enormous. 

 " To arrive at something like an estimate of the value 

 of the perspiratory system," says Mr. Erasmus Wilson, 

 " I counted the perspiratory pores on the palm of the 

 hand, and found 3,528 in a square inch. Now each 

 of these pores being the aperture of a little tube of 

 about a quarter of an inch long, it follows that, in a 

 square inch of skin on the palm of the hand there 

 exists a length of tube equal to 882 inches or 7 3! feet. 

 The number of glands in other parts of the body is 

 sometimes greater, sometimes less than this ; 2,800 

 may be taken as the average number of pores in each 

 square inch throughout the body. Now the number 

 of square inches of surface in a man of ordinary 

 stature is about 2,500 ; the total number of pores, 



* Carpenter's " Principles of Human Physiology," p. 851, note. 

 Sixth Edition. 



