O EVENINGS AT THE MICROSCOPE. 



Running through the very centre of the fibrous portion 

 may be sometimes discerned a dark slender line, which 

 is a sort of pith {medtdla), composed of minute roundish 

 cells, filled with air, and arranged in two or three rows. 



nOG 8 BRISTLE. 



The bristles of the Hog bear much resemblance to 

 the human hair. On this slide is one, which you per- 

 ceive is just thrice as thick as the hair that we have 

 been examining, or i\-^i\i of an inch in diameter. The 

 sinuous lines across the surface are proportionally far 

 finer and closer together, and no saw-teeth are visible 

 at the edge, the most delicate adjustment showing only 

 a minute undulation in the outline ; that is to say, the 

 overlapping scales are far thinner, and therefore their 

 terminations are nearer together, in the hair of the 

 Swine than in that of Man. I will now show you a 

 transverse section of a similar bristle, which I will ob- 

 tain thus : I take this old brush, and with a razor cut 

 off one of the bundles of bristles, close to the wood ; 

 then I take off as thin a shaving as I can cut, wood, 

 bristles, and all : I repeat the same operation two or 

 three times. Now, picking out the shavings of wood, 



