146 The Microscope. 



ELEMENTARY DEPARTMENT 



THIRD LESSON. 



" CLEANLINESS IS AKIN TO GODLINESS." 



OCR APING. — In the last lesson we mentioned the valuable aids to 

 '^ be obtained from teasing, not the least of which was the separa- 

 tion of the various elements composing a tissue, thus facilitating 

 examination. In this lesson we shall discuss another method which 

 will serve oftentimes better than teasing for the isolation of the 

 special cells of many organs. This is by scraping. By this method 

 the connective tissues which form a large part of eveiy animal 

 stracture, are, in a great measure, left behind, and only the cells 

 held in their meshes and special to the organ, are removed. The 

 process is very simple and can be described with few words. 



In the case of the more solid organs like the spleen, liver 

 and kidney, cut into their substance, and then, with a dull blade and 

 from the freshly-cut surface, gently scrape off a little of the tissue. 

 Of this scraping take a portion, the size of a pin's head, tease out 

 in the normal salt solution and examine under cover. Tumors and 

 other pathological growths can be treated as above described. 



The method is best adapted, however, for the studying of 

 mucous surfaces and of the epithelieum which covers them. Scrape 

 the cleansed surfaces of the skin, tongue, oesophagus, intestines, 

 bladder, etc., and examine small portions in the salt solution. 



The beginner may find some difficulty at first in that the pre- 

 pared specimen will be filled with cells and debris and consequently 

 too opaque for satisfactory study. This state of things can never 

 arise, however, if the specimen is thoroughly diluted with the salt 

 solution. We suggested above that a portion of material the size 

 of a pin's head be used. Even this will often be too much. Most 

 satisfactory results will generally be obtained if the portion to be 

 examined be no larger than is easily visible, and this to be separated 

 out in three or four drops of solution. In a well-prepared specimen 

 the cells will be seen in a state of perfect isolation, and can be ex- 

 amined to good advantage. 



This scraping method is best employed with fresh material, but 

 will do good sei-vice in specimens which have undergone partial 

 hardening in Muller's fluid or alcohol. 



It is hoped that the beginner will patiently mount and care- 

 fully examine scrapings from the various organs and mucous sur- 

 faces. If a live frog be obtainable, very pretty examples of active 



