MICROSCOPICAL TECHNIQUE. 77 



mass and the pins drawn through the cork, when it is ready for 

 sectioning. This method offers many advantages in that several 

 objects may be cut at the same time ; drawings may be made 

 after orientation ; the objects are transferred from one solution to 

 another more rapidly, etc. 



In cutting, care should be taken that the knife is placed as 

 obliquely as possible and kept constantly wet with 70 per cent, 

 alcohol. For this purpose an ordinary pipette, provided with a 

 large rubber bulb, is used. As fast as cut, the sections are drawn 

 back on the blade of the knife by means of a needle, and arranged 

 in a single row until the blade is filled. To remove these, a heavy 

 paper spatula is placed directly upon the section, to which it 

 adheres, and may be drawn off the edge of the knife and trans- 

 ferred to the slide. By slight pressure together with a rolling 

 movement, the section is left in the desired position. Sufficient 

 alcohol is kept on the slide to prevent drying, but not enough to 

 allow the sections to float. When the requisite number have been 

 arranged, they are covered with a strip of toilet-paper, which is 

 held on the slide by winding it with fine thread. The sections 

 being thus firmly held in position may be stained, etc. They 

 should not be placed in absolute alcohol, but cleared in 95 per 

 cent., in a mixture of equal parts of bergamot oil, cedar oil, and 

 carbolic acid. When cleared, the excess of fluid is removed by a 

 piece of blotting-paper. With gentle pressure, sections which are 

 by chance loose are firmly fixed in position, the thread is now cut, 

 the strip of paper rolled back, and balsam and cover applied. 



If the object is stained iti toto — which is often the case — much 

 time may be saved by the following method : — The stained object 

 is embedded in the usual manner, but after hardening in chloro- 

 form and removing the paper, the celloidin block is transferred to 

 95 per cent, alcohol for twenty-four hours, then to carbolic acid 

 (Bumpus, Amer. Nat., January, 1892, advises the use of thymol) 

 or glycerine, in which it becomes as transparent as glass (Mr. 

 Eycleshymer finds that the clearing mixture answers the same 

 purpose as the carbolic acid, but requires a little longer time). 



Orientation is now accomplished with the greatest ease. In 

 cutting, the knife is wet with the clearing medium given above. 

 The sections may be arranged in serial order on the knife-blade 



