14 MICRO-ORGANISMS AND DISEASE. [CH. r. 



to freeze and to cut. Fresh tissues are at once cut with the 

 freezing microtome, the sections placed in a 0-6 per cent, 

 saline solution, floated out and well spread out, and then 

 stained by transferring them in this condition, i.e. well 

 spread out, into a watch-glass containing the dye. The 

 sections of hardened tissues are floated out in water, well 

 spread out, and then transferred to the dye or dyes as the 

 case may be. 



It is necessary to prevent too much shrinking of the 

 sections, especially those of fresh tissues ; for this reason it 

 is advisable to float the sections in the saline solution or water, 

 as the case may be, on a broad lifter or spatula, to spread 

 them well out upon it, and to transfer them carefully into 

 the dye, then into the dish with water used for washing off 

 the excess of the dye, to transfer them, well spread out on the 

 lifter, to alcohol, then after several minutes to oil of cloves, 

 and finally on to a glass slide, on which they are mounted in 

 the usual manner with Canada-balsam solution, the excess of 

 clove-oil being previously drained off. 



It is advisable, although not absolutely essential, to keep 

 the sections in a well-spread-out condition for a few seconds 

 in alcohol before placing them into the dye. 



Microphotography, by which microscopic specimens of 

 bacteria are photographed, have hitherto yielded results so 

 unsatisfactory, that even Koch, who first introduced it, has 

 abandoned it in lieu of accurate drawings made in the usual 

 manner. 



