MICROSCOPICAL TECHNIQUE. 75 



hide the junction of the cover-glass and cell-wall. When this 

 latter step is accomplished, the mount is essentially complete, but 

 no one who has a pride in his work will leave the slide unstriped. 

 There is no more beautiful slide than one formed of white cement 

 ringed with black. Properly labelled and cleaned, the slide is 

 ready for the cabinet, and if the due amount of care has been exer- 

 cised in its preparation, it will always be a source of pride and 

 pleasure to its owner." 



Notes on Celloidin Technique. —Mr. A. C. Eycleshymer gives 

 the following as the result of his experience in working with cel- 

 loidin. The prepared fragments of celloidin are placed in an air- 

 tight chamber, a four-ounce wide-mouth bottle being very suitable 

 for this purpose, and enough ether-alcohol (equal parts of acid-free 

 sulphuric ether and absolute alcohol) poured in to cover the frag- 

 ments. The ether-alcohol should be added until no celloidin 

 remains undissolved. It should finally be of the consistency of 

 very thick oil. This solution may be labelled No. 4. No. 3 

 consists of two parts of No. 4, diluted with one part of ether- 

 alcohol ; No. 2, by proceeding in a like manner with No. 3. No. i 

 is a mixture of absolute alcohol and sulphuric ether in equal parts. 



The object to be embedded is transferred from 95 per cent, 

 alcohol to solutions i, 2, 3, 4 successively, in each of which it 

 remains from a few hours to days, dependmg upon the size and 

 permeability. 



In embedding, unless orientation is desired, the ordinary 

 paper-box is best. A thin plate of lead is placed in the bottom 

 and the embedding solution poured in. The object is taken from 

 the same solution, and with needles wet in ether placed in the 

 desired position. Fine needles may be passed through the box to 

 support the object. 



In hardening, Viallare's chloroform method is preferable. An 

 air-chamber should be filled with chloroform. After the mass is 

 thoroughly hardened — which requires about twenty-four hours — it 

 is removed, the paper cut from the sides, and transferred to 70 per 

 cent, alcohol for a few hours. 



It is now ready for sectioning. Blocks are trimmed to fit the 



* American Naturalist, xxvi. (1892), pp. 354 — 357. 



