1MBKDDING MKTHODS (PARAFFIN). 115 



140. Recapitulation of the Paraffin Method, as recommended 

 to be practised for small objects. Put into a small test-tube 

 enough oil of cedar to cover your object. On to the oil 

 pour carefully the same quantity of absolute alcohol. Take 

 your (already dehydrated) object and put it carefully into 

 the alcohol. Leave it until it has sunk to the bottom of the 

 cedar oil. Wait till the refraction lines, 106, have vanished. 

 Then put it into paraffin kept at melting-point in a watch 

 glass. Let the paraffin be of the very lowest melting-point 

 that will give sufficiently thin sections, and to this end work 

 in a cool place. After a time change the paraffin (i. e. put 

 the object into a fresh watch glass with clean paraffin) once,, 

 or twice if the object be at all large. As soon as the object, 

 is thoroughly soaked with paraffin float the watch glass on 

 cold water. When cool, cut out a block of paraffin contain- 

 ing the object, and fix it with a heated needle on a cone of 

 paraffin already mounted on the object- carrier of the micro- 

 tome. 



Trim and orient the block and knife according to circum- 

 stances, as directed under 6, 134. Cut the sections, singly 

 if desired, or for convenience in ribbons. Collodionise if 

 necessary. When cut always flatten and expand on water, 

 138. Fix them in serial order on a slide by one of the 

 methods given in*the chapter on " Serial Section Mounting/' 

 the water method by preference if they have to be stained. 

 Warm and remove the paraffin with xylol. Stain, or mount 

 directly. 



Paraffin Masses. 



141. Pure Paraffin. It is now almost universally admitted 

 that pure paraffin forms an imbedding mass greatly superior 

 for ordinary work to any of the many mixtures with wax and 

 the like that used to be recommended. A paraffin melting 

 at 45 C. is that which in my experience gives the best 

 results so long as the temperature of the laboratory is between 

 15 and 17 C. ; whilst for a temperature of 22 C. a paraffin 

 melting at 48 is required. And for higher temperatures a 

 still harder paraffin, of over 50 melting-point, is required. 



Paraffin of various melting-points is easily found in com- 

 merce. Intermediate sorts may be made by mixing hard 



