THE MICROSCOPE. 245 



be left out of the rows of red disks, and, if the highest 

 power be used, will be seen to change their shape con- 

 stantly. 



17. If you scrape with a dull knife the inside of the 

 cheek, the flattened scales of " pavement epithelium," or 

 of the insensible covering which, analogous to the scarf- 

 skin on the outer surface of the body, lines the cavities of 

 its interior, may be readily studied. They have the appear- 

 ance of transparent tiles, each enclosing a round or oval 

 body, called its nucleus. Dandruff and the scrapings 

 from the skin of the body are composed of scales like 

 those of the mouth, but they differ somewhat in being 

 hardened by horny matter, and in having a very faint 

 central body or nucleus. 



18. The Tissues of the Inferior Animals. The 

 warm-blooded animals do not differ in the tissues, or mi- 

 croscopic structures, that compose them, but only in the 

 amount and arrangement of these tissues. Milne Edwards 

 says these tissues " do not differ much in different animals, 

 but their mode of association varies; and it is chiefly by 

 reason of the differences in the combination of these asso- 

 ciations in various degrees, that each species possesses the 

 anatomical properties and characters which are peculiar 

 to it." 



19. Hence the butcher's stall will furnish all the mate- 

 rials for the study of the microscopic tissues. The struc- 

 ture of the heart, lungs, liver, brain, and muscle may all 

 be studied, and well studied, by using minute pieces of 

 the flesh of the lower animals, especially of the quadru- 

 peds. Such portions of these animals as are not exposed 

 for sale can be readily obtained by order from the slaugh- 

 ter-house. To examine with the powers of which we 

 have been speaking, it is only necessary to cut off exceed- 



1 7. Examination of the scales of the mouth ? Dandruff ? 



18. In what, as respect* the tissues, do the warm blooded animals differ? 

 Statement of Milne Edwards ? 



19. How to procure materials for the study of the tissues of man ? 



