216 



THE MICROSCOPE AND ITS LESSONS. 



the photographer calls it, recalls the image; but what 



causes the retention of the image forty or fifty years 



after? 



We may see multitudes of invisible muscular fibre?, 

 through which once ran the 

 nerves carrying the pictures of 

 the outer world to the brain of 

 some member of our race dis- 

 integrated bundles of invisible 

 threadlets they are. These 

 extremely delicate radiating 

 fibres average the fifteen - 

 thousandth part of an inch in 

 diameter. They are aggregated 

 into flattened bundles, and ap- 

 pear to be mechanically held 

 together by a countless number 

 of teeth, each one interlocking 

 with the other. 



And here you have what 

 perhaps you will say is the most 

 interesting of all our anatomical 

 objects, the human skin from the 

 hand. Observe, this is stained 

 with three different colours, so 

 that the various parts may be 



Vertical section of human skin, more easily distinguished. The 



cnS2fT& inneHr frue^in" 6ntil ' e bod J is COV ^d with this 



c, the coii of a sweat-duct, finding its wonderful clothing, which is 



^,x* 



outlet on the surface, a ; between a 

 and b is seen the pigm 

 give colour to the skin 



and 6 is seen the pigment-cells which composed of two layers an 



inner, the vera cutis, or true 

 skin, which usually makes up the largest part of its 

 thickness ; and the epidermis, which covers it. These 

 two skins are separated by a thin bed of gelatinous sub- 



