218 MOUNTING OBJECTS IN CANADA BALSAM. 



more will in this case be necessary, than to lay some liquid Balsam 

 on the surface of the section, to warm it gently, and then to 

 place on it a thin-glass cover of suitable dimensions, gently pressing 

 this down wherever the balsam happens to be thickest, and en- 

 deavouring to drive all air-bubbles before a wave of liquid, until 

 they are entirely expelled, or at any rate are driven beyond the 

 margin of the section. If this operation be not at once successful, 

 — either a few large air-bubbles, or a great number of smaller ones, 

 which cannot be got-rid-of by gentle pressure, being visible between 

 the surface of the section and the covering -glass, — it is better at 

 once to remove the cover by gentle warmth applied to its upper sur- 

 face, and to repeat the operation with an additional supply of balsam, 

 rather than to attempt to drive-out the bubbles by any manipula- 

 tion. Whatever treatment be adopted, special care should always 

 be taken not to apply so much heat as to melt the hard balsam be- 

 neath the section, or to boil the thin balsam above ; and this may 

 be best managed by turning the slide with its face downwards, so 

 that the heat may be applied directly to the thin-glass cover and 

 to the balsam in contact with it, instead of acting on this through 

 the slide and the object attached to it. If the heat should unfor- 

 tunately be carried so far as to boil the cement beneath the section, 

 there will be little chance, if its area be large, of getting- rid of the 

 bubbles thus produced, without removing it altogether from the 

 glass to which it was attached, or, at any rate, without pushing it 

 along the glass in such a way as to slide it away from the bubbles ; 

 in that case, the part towards which it is moved should always be 

 well supplied with balsam, and the bubbles that remain should be 

 drawn away or broken with the needle-point ; after which, the 

 section being slid-back to its original position, it is probable that 

 no bubbles may be found beneath it. — In cases, however, in which 

 the appearance of the preparation is an object of much considera- 

 tion, and in which the tenacity of the substance and the small size 

 of the section prevent much risk of its breaking in the transfer, it 

 may be loosened from the glass to which it was first attached, either 

 by heat, or by soaking in Ether or Chloroform. The former, being 

 the simplest and readiest method, is the one most commonly prac- 

 tised ; the only difficulty lies in lifting-off the specimen without 

 breaking it ; and this may best be done by means of a camel-hair 

 brush dipped in Oil of Turpentine. The glass to which the section 

 is to be transferred should have a large spot of liquid balsam laid 

 in the proper place ; the object is to be laid on this, and its upper 

 surface covered with the like balsam ; and then, the thin-glass 

 cover being placed upon it, this is to be gently pressed down in the 

 manner already described. If Ether or Chloroform be had recourse 

 to, the slide should be placed in a wide-mouthed bottle of that 

 liquid, which should then be corked or stopped ; and after a time 

 the section will be found to be lying detached in it, whence it may 

 be taken -up either by the forceps or by a camel-hair brush. — Such 



