56 BACTERIOLOGY 



The soluble cotton sold by dealers in photographer's supplies serves 

 as well as the expensive preparation known as celloidin. To 

 make collodion, dissolve it in equal parts of alcohol and ether. 

 Soluble cotton is also called pyroxylin, and is a kind of gun-cotton. 



Imbedding in Paraffin. — {a) Pieces of tissue 2 to 3 mm. thick 

 which have already been fixed in alcohol or formaldehyde are to 

 be placed in absolute alcohol for twenty-four hours. 



(&) In pure xylol one to three hours. 



(c) In a saturated solution of parafi&n in xylol one to three hours. 



{d) In melted paraffin having a melting-point of 50° C, which 

 requires the use of a water-bath or oven> one to three hours. The 

 xylol must be entirely driven off, and the tissue thoroughly 

 infiltrated. 



(e) Change to fresh paraffin for one hour. 



(/) Finally, place the tissue in a small dish or paper box and 

 pour the melted paraffin about it. HarderTas quickly as possible 

 with running water. It is important to fix the piece of tissue 

 in a suitable position, if the position is of importance, before 

 pouring in the melted paraffin. Sections of exquisite thinness 

 may now be cut. The knife need not be wel. Paraffin im- 

 bedding is especially desirable when serial sections are to be made. 



In order to mount the sections, proceed as follows : 



(a) Place the sections on water in a porcelain capsule. 

 Warm slightly, when the sections will flatten. Smear the surface 

 of a slide with a very thin layer of Mayer's glycerin-albumen 

 mixture. Dip the slide under the sections; lift them; and then 

 drain off the water, leaving the sections in their proper positions. 

 Let them dry for some hours in the incubator, and they will be 

 firmly fastened to the slide. 



GLYCERIN-ALBUMEN MIXTURE (MAYEr) 



Equ&.l parts of white of egg and glycerin are thoroughly mixed, and then filtered. 

 Add a little gum-camphor to preserve. 



(6) Dissolve out the paraffin in one of the numerous solvents 

 (xylol, a few minutes). 



