154 THE MICROSCOPE. 



ferred into absolute alcohol, which must be changed several times. 

 When this end has been accomplished, it is put into spirits of tur- 

 pentine, also to be removed twice at least for large pieces. It is 

 then placed in a saturated solution of parafifin in spirits of 

 turpentine, where it is again left for several days — the time 

 varying with the size of the specimen. Next, it is removed and 

 laid on filtering paper, that the turpentine may evaporate; the 

 paraffin remains and fills the crevices, blood and lymph 

 vessels, &c. When sufficiently dry, it is embedded in a mixture of 

 paraffin and mutlon suet — the proportions of which vary with 

 the seasons. In summer, pure paraffin will be found neces- 

 sary. The paraffin should always be heated on a water bath and 

 it will be found very convenient to throw the piece to be embedded 

 into the hot fluid mixture, so that it gets thoroughly soaked and 

 when cooled off, forms an inseparable mass of equal consistence 

 with the paraffin. You will never find any tissue, not even embry- 

 onical, to spoil by exposing it to a moderate heat, while in the fluid 

 paraffin. 



It is then ready to be cut dry, and can be preserved in this state 

 any number of years. 



For cutting, it is best to employ a sledge microtome, made by 

 Hsertel, in Breslau, after designs by Dr. Long, which enables you to 

 make very long sections of equal thickness — from yf^th of a milli- 

 metre upwards. When properly constructed, it is the most perfect 

 instrument of its kind known and the cost of it with two knives and 

 a case is in Germany, at the makers, 75 marks, equal to about $19. 

 The section thus cut is transferred to a slide, where it frequently 

 has to be unrolled, the only drawback to the method, as it requires 

 some dexterity of manipulation. To dissolve the paraffin remain- 

 ing around and in the section a few drops of a solution of creosote 

 and turpentine (in the proportion of one to four) are added, and 

 when this has been removed from the glass by wiping or by drawing 

 it up with filtering paper, it is enclosed in either damar varnish or 

 Canada balsam. 



It happens pretty frequently that the specimen, when 

 in the paraffin, is found not to adhere to it. In that case throw 

 the v.hole piece back into the hot paraffin and suet mixture 

 and embed it then anew. By this manipulation you get rid of 



