III, 2. Minot: Notes on Histological Technique. 175 



box shüuld be considerably deeper tlian tlie specimen so that when the 

 latter is imbedded half or tliree quarters of an incli (2 cm) of celloidine 

 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 

 hardening should be as cold as possible, for the bubbles in the celloi- 

 dine are apparently due to the too rapid extraction of the ether; their 

 formation is certainly hindered by lowering the temperature. 



4. Mounting celloidine sections. For clarifying celloidine 

 sections various esseutial oils have been recommended 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 more satisfactorily ; if the 

 sections are thoroughly dehydrated in 96 % alcohol, they will clear up 

 almost instantly ; if they are not quite thoroughly dehydrated a little 

 cloudiness appears and the celloidine puckers considerably. Alcohol 

 stronger than 96"/, or weaker tban 95 "/o ought not to used for this 

 purpose. 



Much more satisfactory is a mixture, for which we are indebted 

 to Dr. E. K. DüNHAM, working in the pathological laboratory of the 

 Scheol, and which he has very kindly conseuted to let me communicate 

 here. This mixture is three parts of white oil of thyme with one part 

 of oil of cloves ; I am inclined to think that 4 : 1 may prove an even 

 better proportion. The mixtiu'e clarifies the sections very readily and 

 softens the celloidine just enough to prevent the puckering, which is 

 so annoying with thyme alone. Mr. Dünham has certainly made a 

 very welcome addition to the technique of the celloidine method. 



To mount 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 num- 

 bered dishes to preserve their order; they are then staiued, either all 

 alike or as is often advantageous by various methods; dehydrate 

 thoroughly in alcohol 5 place the sections on the slide in the desired 

 Order, keeping them covered with alcohol; wheu they are arranged 

 the alcohol is drained off by tilting the slide ; it is necessary that the 

 sections on the slide should be really dehydrated, hence it is sometimes 

 necessary to wash them again with fresh 96% alcohol, as they lie upon 

 the slide. The sections are now well covered with a perfectly clear 

 10 to 12% Solution of refined shellac, and the slide at once exposed 

 to a gentle warmth (30 to 40" C) until the shellac is completely dried. 



