Methods of Microscopical Research 



may be e 



asily fixec 





a larger block of 



paraffine. 





V. Cutting. 





Objects are cut dry with a microtome, 1 and the rolling of the 

 sections may be prevented by holding a 

 r\ ^ /K thin narrow spatula over the edge of the 



/ \ \ / \ knife while cutting. The spatula may be 



I J I / LJ \ made of brass, in the form of Fig. i; of pa- 



ll Q per fastened to a flattened needle as indi- 



\ / | \ I cated in Fig. 3. The spatula should be bent 



I ! " H-H slightly (Fig. 2), and its convex face held 



over the paraffine without pressure. A 

 small brush, slightly flattened, is used for the same purpose in 

 Leipsic. 



VI. Giesbrecht's Methods. 

 (1) Transferring from Alcohol to a solvent of Paraffine?— -To 

 avoid shrinkage in transferring tender objects from alcohol to 

 chloroform or an oil, pour a little absolute alcohol into a small 

 glass tube, place the canular end of a pipette containing the sol- 

 vent below the surface of the alcohol, and allow a few drops to 

 flow from it to the bottom of the tube ; into this tube let fall, by 

 the aid of another pipette, or a small spatula, a few drops of abso- 

 lute alcohol containing the objects to be imbedded. The objects 

 will sink through the alcohol, which, being the lighter fluid, has 

 taken a superjacent position, and rest on the upper surface of the 

 fluid expelled from the first pipette. Most of the alcohol may 

 now be removed by a pipette, and the objects left to sink gradu- 

 ally into the heavier fluid at the bottom of the tube. In this way 

 the replacement of the alcohol contained in the objects by an oil, 

 or some solvent of paraffine, is much retarded, and thus the dan- 

 ger from shrinkage reduced to a minimum. 



Where chloroform is preferred to creosote or oil of cloves, a 

 little ether (aether sulfuricus QH.,0) should be added, as many 

 objects will not sink in pure chloroform. 



To replace alcohol by a solvent of paraffine, and then by par- 



1 An improved form of Tboma's microtome is made by Rudolph Yung, Heidelberg, 

 Hi 1 tras e 15. The carrier is moved by a micrometer screw, and the holder can 

 be adjusted in any desired position. A full description of the instrument vv.th a 

 the recent improvements will soon be given by Dr. Mayer. 



2 Giesbrecht. " Zur Schneide-Technik," in Zoolog. Anzeiger, 1881, No. 9 2 - 



