44 HOW TO WORK 



for heating glass slides, in order to fix on the glass cells with the aid 

 of marine glue, for mounting objects in Canada balsam, and for other 

 purposes, where a uniform degree of heat is required to be applied to 

 glass, which is very liable to crack if exposed suddenly to the naked 

 flame. These different pieces of apparatus have been figured in 

 pi. XIV, fig. 68. 



"J3. The Water Bath is of great use for drying objects previous to 

 mounting them in Canada balsam. The object may be placed in a 

 small porcelain basin, or large watch-glass, or it may be simply laid 

 upon a flat plate. The basin or plate is then placed over the vessel 

 containing water to which heat may be applied, fig. 73. In order 

 that vessels of different sizes may be heated upon the bath, it is con- 

 venient to have a few pieces of thin copper plate, with holes of dif- 

 ferent sizes cut in them, adapted for watch-glasses and small vessels, 

 fig. 74. The advantage of drying by a steam heat consists in there 

 being no danger of destroying the texture of the object by the appli- 

 cation of too high a temperature. A water-bath may be very readily 

 made by placing two porcelain basins one above the other, water 

 being poured into the lower one. These may be supported upon a 

 tripod or upon one of the rings over the spirit lamp, fig. 70. 



For Cutting thin Sections of Tissues and Dissection. 



74. Scalpels. It will be convenient to have three or four ordi- 

 nary dissecting knives or scalpels for general use. One should be 

 strong for the purpose of cutting hard substances. 



75. Double-edged Scalpels. For cutting thin sections, a knife of 

 the form of a very narrow lancet will be found useful, and where only 

 sections of small dimensions are required, this will answer all the 

 purposes of Valentin's knife. In cases, however, where a section is 

 wanted of considerable size, the latter instrument must be used. The 

 double-edged scalpel should be very thin, pi. XIV, fig. 75. Beautiful 

 scalpels of this form have been made for me by Messrs. Weiss, of the 

 Strand. In making a section, after cutting a clean surface, the point 

 is made to perforate the surface, and carried along at a proper depth, 

 so as to cut its way out. The width of the section may then be 

 increased by carrying the knife from side to side. 



7. Section Knife of a TV'ew Form. A new section knife has 

 been devised by Deputy Inspector-General Lawson, for cutting very 

 thin sections of soft tissues. The general form of the knife is repre- 

 sented in pi. XIV, figs. 76 and 77. It is fully described in my Archives, 

 vol. Ill, p. 286. 



