230 



THE AMERICAN MONTHLY 



[December, 



For imbedding are needed — 



a. Mixture of equal parts of ether 

 and alcohol. 



b. A thin solution of celloidine in 

 a. This solution should be syrupy 

 and flow easily. 



c. A thick solution of celloidine in 

 a, of about the consistency of thick 

 molasses. 



d. An imbedding- box, made by 

 fastening a roll of paper around a 

 cylindrical cork with a pin. 



e. A sinker, which may be conve- 

 niently made by casting a piece of 

 lead around a wire nail. 



f. Alcohol of So to 85 per cent. 



In regard to these, all of which are 

 in familiar use, the following points 

 may be noted : — The mixture of ether 

 and alcohol is very difficult to keep, 

 and ought to be renewed every few 

 days, because of the loss of ether. 

 For the same reason the celloidine 

 solutions are best used fresh ; accord- 

 ingly, when from the loss of ether the 

 solution begins to turn unclear or 

 milky, it may be poured out and al- 

 lowed to dry completely, and then 

 redissolved. Dirt may be removed 

 from the solution by settling and de- 

 cantation. The imbedding box is 

 like that recommended by Bloch- 

 mann ;* is is, however, unnecessary 

 to roughen the cork, and it is advan- 

 tageous to cover the end, which 

 makes the bottom of the box, with 

 celloidine. The celloidine ought to 

 be thoroughly- dried before the cork 

 is used, so as to form a firm coat to 

 prevent the air in the cork from es- 

 caping to form bubbles in the celloi- 

 dine. The box should be consider- 

 ably deeper than the specimen, so 

 that when the latter is imbedded half 

 or three-quarters of an inch of celloi- 

 dine shall cover it, so as to allow 

 room above the specimen for the 

 bubbles to accumulate, which form 

 during the hardening in alcohol. It 

 is convenient to make the sinker with 

 a flat bottom. The alcohol for hard- 

 ening should be as cold as possible, 

 for the bubbles in the celloidine are 



*Zietsch. f. w. Mikros., i, p. 226. 



apparently due to the too rapid ex- 

 traction of the ether ; their formation 

 is certainly hindered by lowering the 

 temperature. 



Mounting celloidine sections. 

 For clarifying celloidine sections, 

 various essential oils have been rec- 

 ommended, but none of them are 

 entirely satisfactory so far as we have 

 tried them, for they either attack the 

 celloidine-like oil of cloves, or cause 

 it to pucker like oil of origanum. 



Chloroform works much niore sat- 

 isfactorily. If the sections are thor- 

 oughly dehydrated in 96"o alcohol, 

 they will clear up almost instantly ; 

 if they are not quite thoroughly de- 

 hydrated, a little cloudiness appears, 

 and the celloidine puckers consider- 

 ably. Alcohol stronger than 96"n, 

 or weaker than 95 "m, ought not to be 

 used for this purpose. 



Much more satisfactory is a mix- 

 ture, for which we are indebted to 

 Dr. E. K. Dunham, communicated 

 with his consent. This mixture is 

 three parts of white oil of thyme 

 with one part of oil of cloves. I 

 am inclined to think that 4 : i may 

 prove an even better proportion. 

 The mixture clarifies the sections 

 very readily and softens the celloi- 

 dine just enough to prevent the 

 puckering, which is so annoying 

 with the thyme alone. Dr. Dun- 

 ham has certainly made a very wel- 

 come addition to the technique of the 

 celloidine method. 



To mount the series of celloidine 

 sections, I venture to unreservedly 

 recommend the following method: — 

 The fastening of the sections to the 

 slide with shellac. The sections, as 

 they are cut, are placed in numbered 

 dishes to preserve their order ; they 

 are then stained, either all alike or, 

 as is often advantageous, by various 

 methods ; dehydrade thoroughly in 

 alcohol ; place the sections on the 

 slide in the desired order, keeping 

 them covered with alcohol ; when 

 they are arranged the alcohol is 

 drained ofl" by tilting the slide. It 

 is necessary that the sections on the 



