3 82 



PREPARATIONS BY THE PARAFFIN METHOD [Ch. XI 



Ribbons on trays may be kept a long time, three or four years at 

 least, if they are stored in a cool place. The sections do not flatten 

 out quite as well after standing a long time as they do soon after they 

 are made. 



§ 618. Paraffin ribbon winder. — As most embryos and many or- 

 gans which are to be cut entire make ribbons much longer than the 



slide tray, it is necessary to cut the ribbons 

 — -f into segments usually as they are made. If 



i llinium 



Fig. 226. Leveling 

 Metal Table for 

 Spreading Sections and 

 for Imbedding in Par- 

 affin. 



one grasps the ribbon with fine forceps and 

 carries it out from the microtome it is liable 

 to break from its weight when it gets long. 

 The spread of the arms prevents a very long 

 section also. If one has to stop in making a 

 series there is liable to be a section too thin 

 or too thick when one begins again, and fre- 

 quently a section is lost. To overcome this very radical defect 

 McClung and Hance have devised what they call a "Paraffin Ribbon 

 Winder." This consists of a cylinder (mailing box on an axle) on 

 which the ribbon is wound as cut, just as thread is wound on a spool. 

 (For figures and descriptions, see Anatomical Record, June 20, 1916, 

 pp. 523-526; Trans. Amer. 

 Micr. Soc, Vol. XXXII, 

 1913, PP- 297-299.) 



§ 619. Spreading the 

 sections on water. — Par- 

 affin sections are almost in- 

 variably slightly wrinkled 

 or folded in cutting. To 

 remove the wrinkles one 

 takes advantage of the ex- 

 pansion of paraffin when 

 it is warmed. The sec- 

 tions may be floated on warm water, when they will straighten out 

 and become smooth, or the usual method is to stretch them on the 

 slide upon which they are to be finally mounted. 



By spreading sections on a wet slide a double operation is per- 



Fig. 227. 



Alcohol Lamp in a Vertical and 

 an Inclined Position. 



