174 The Microscope. 



As has been said, the great desideratum is comparatively anhy- 

 drous alcohol. The alcohol used for this purpose should be kept in 

 a tightly-corked bottle and in a dry place, and when poured into the 

 salt-cellar for use should be quickly covered. All this to prevent 

 the absorption of moistm-e from the atmosphere. The vessel should 

 be carefully dried and the specimen, before being immersed, should 

 ba dipped into ordinary alcohol in order to remove the grosser por- 

 tion of water. If carefully done, ten minutes will be sufficient time 

 to prepare the specimen for the oil; but it will be as well to leave it 

 for several hours. When the oil has rendered it perfectly clear — 

 which takes from five to ten minutes — 'it is mounted in balsam and 

 laid away to dry. 



Now as to the manner of doing all this. The specimen can be 

 handled in the silver solution and waved around gently in the dis- 

 tilled water when being washed, by means of a needle fixed in a 

 holder passed beneath it. When in the solution — and this will 

 apply to all stains mentioned hereafter — and when being exposed to 

 the light, it should be carefully flattened out, that every portion 

 of the surface receives equal treatment. Before removing to alcohol 

 is the time to see that all wrinkles and overlapping portions are cor- 

 rected. To accomplish this, take a rectangular piece of paraffine, or 

 tissue-paper about one-half again as long and somewhat wider than 

 the specimen, grasp lengthwise with the forceps and gently pass 

 under the object. With a fine camel's-hair brush carefully smooth 

 out and arrange it on the paper and then withdraw slowly from the 

 water. With a little practice this operation can be easily per- 

 formed, as the specimen is soft and pliable. Now dip it quickly 

 into the ordinary and then immerse slowly in the absolute alcohol, 

 which has been previously put into a salt-cellar. Do not now urge 

 the specimen from the paper, but wait a moment and the alcohol 

 will set or harden it ao that it will generally slide off of its own 

 accord. If not, a gentle to-and-fro motion will sufiice. 



After becoming dehydrated it can be removed in the same man- 

 ner to the oil or turpentine. If the object is a small one, however, 

 it can be lifted out with a needle, as it will not curl or wrinkle, hav- 

 ing been stiffened by the alcohol. Before placing in the clearing 

 medium it will be well to remove some of the alcohol by touching 

 the specimen to a blotter. 



Note. — As to the choice between the essential oils and turpen- 

 tine, it may be said that the former has the advantages of clearing 

 the specimens just enough and leaving them tolerably pliable; their 

 disadvantages are their high cost and color. The latter requires 



