l68 CLINICAL BACTERIOLOGY AND HiEMATOLOGY 



taken from the bottle containing the melted paraffin with a pair of 

 forceps (previously warmed, so as to prevent the paraffin from 

 setting upon the points), and placed in the paraffin in the pill-box. 

 It is necessary to see that the surface from which sections are to 

 be cut should be placed downwards. The box is then filled up 

 with melted paraffin, and placed in a cool place or surrounded with 

 water. The moment a firm film has formed over the surface the 

 whole is plunged in cold water to hasten the setting of the paraffin ; 

 the more rapidly this takes place the better will the block cut. 

 When the paraffin mass has hardened completely throughout, it 

 is trimmed into shape, taking care that the edges of the surface 

 which is to be cut are accurately parallel. 



Cutting the Sections. — For cutting sections in paraffin no 

 microtome can be compared with the Cambridge Rocker, but 

 very excellent results can be obtained by the use of the 



Fig. 41. — Clamp for holding Wooden Block with the Paraffin Block. 



Cathcart microtome already mentioned. The paraffin block 

 containing the piece of tissue is mounted on the freezing- plate 

 of the microtome (which must be heated, and the lower surface 

 of the block pressed upon it), and the sections cut in the manner 

 described ; a very sharp knife is essential, and the stroke must be 

 quicker and sharper than is the case when frozen sections are 

 being cut. In another form of the microtome a special inner 

 tube is provided for cutting sections by the paraffin process. 

 The blocks are retained in place by a clamp, and appear in the 

 same position as that occupied by the mass of frozen gum. As 

 the paraffin is not sufficiently hard to be gripped by this clamp, 

 they must first be mounted on a piece of wood of a suitable size 

 and shape. This can be cut out of a piece of firewood, and 

 should have one surface left rough ; this surface must be dipped 

 in melted paraffin, and the under surface of the block partially 

 melted in the flame and pressed firmly upon it. The piece of 

 wood is then to be placed in the jaws of the clamp, and the screw 

 tightened up. 



