58 PRACTICAL HISTOLOGY [VII 



Dip the block up to the base in melted paraffin of melting 

 point about 40 C., leave it there for 2 to 3 seconds, then lift it 

 out, and hold it vertically for about 10 seconds for the paraffin 

 to set. Put it aside for a minute or two to cool (or cool it in 

 water, removing afterwards the adhering water). With a sharp 

 scalpel cut away the soft paraffin from the surface to be cut, and 

 from the sides of the block, leaving it only on the sides which 

 will be parallel to the razor edge in cutting. Examine the 

 junction of the hard and soft paraffin with a lens. If the two do 

 not adhere, the process of re-coating should be repeated. 



9. Superficial Imbedding. This can be employed with small firm 

 pieces of tissue. It is often advantageous with portions of the 

 nervous system treated by the Golgi-Bamon method (cp. p. 240). The 

 piece of tissue is placed in 95 p.c. (or absolute) alcohol for 5 to 15 

 minutes. The imbedding mixture consists of 2 parts of hard paraffin 

 and 1 part of vaseline. Sections of this curl less than sections of hard 

 paraffin, and fold less than soft paraffin. 



Take a short oblong or cylindrical block of paraffin-mixture. 

 Scoop out a small hole at an end of it. Take the tissue up with 

 forceps, roll it over on blotting-paper to remove excess of alcohol, but 

 without allowing it to dry, dry the points of the forceps, and place 

 the tissue in the hole in the paraffin. With a warm suction pipette, fill 

 the hole with melted paraffin mixture. Heat a wire or an old scalpel in 

 a Bunsen flame ; and with it remove any bubbles that may be present, 

 being careful not to touch the tissue with the wire when it is over- 

 heated. Let the paraffin cool a little, then cool it further in water. 

 Pare down the paraffin to the surface of the tissue, and level the 

 edges. Blow strong alcohol on the razor from a wash-bottle and cut 

 sections free-hand, removing the section to 95 p.c. alcohol ; the tissue 

 must throughout be kept moistened with alcohol. The sections can be 

 at once transferred to clove oil and mounted, or if the paraffin has 

 penetrated into the outer layers, they may be transferred to absolute 

 alcohol, then to xylol and mounted. If an unstained piece of tissue 

 has been taken the sections may be stained in the usual way. 



