228 MICROSCOPICAL RESEARCH IN THE 



(2) Transferring from Chloroform to Paraffine. — After the 

 objects have become thoroughly saturated with chloroform, the 

 containing tube is placed on a water bath and heated to about 

 50^ C. — the melting point of paraffine ; then a small piece of 

 paraffine is added and allowed to dissolve, and this is repeated 

 until bubbles cease to rise from the objects. To make sure that 

 the chloroform has been fully expelled, the objects may next be 

 transferred to pure paraffine, and left for a few minutes before 

 imbedding.* 



(3) Shellac as an aid in Mounting. — The use of shellac for 

 fixing sections on the slide, introduced by Dr. Giesbrecht,t is a 

 very valuable addition to histological methods. By this method 

 hundreds of small sections may be arranged in serial order, and 

 all inclosed in balsam under the same cover without danger of 

 disarrangement. The method is further extremely useful in 

 mounting larger sections, particularly those composed of loose 

 parts, or parts liable to swim apart. 



The shellac is prepared and used in the following manner : — 

 One part of bleached shellac, % mixed with ten parts absolute 

 alcohol, and filtered. The object-glass is first warmed to about 

 50^ C.,§ and then a thin film of the shellac is laid on by a glass 

 rod drawn once over its surface. Before using, the slide is again 



* For the Hydrozoa, Professor Weismann prefers turpentine to chloroform, as 

 where the latter has been used, the parafifine is liable to be more or less spongy in 

 consequence of bubbles lodged in the tissues. 



Turpentine renders objects brittle, and on this account chloroform will, in 

 many cases, give better results. The spongy state of the parafifine results from the 

 fact that the chloroform has not been allowed to wholly escape. 



In the case of the Actinice, Dr. Andres employs a mixture of turpentine, 

 creosote, and alcohol, using successively mixtures containing more turpentine and 

 less alcohol, thus : — 



t Giesbrecht. " Methode zur Anfertigung von Serien-Praparaten," in Mitthei- 

 lungen a. d. Zoolog. Station, zu Neapel, 1881, p. 184. 



J Dr. Mark informs me that he uses " the bleached shellac in the form in 

 which it is prepared for artists as a ''fixative ' for charcoal pictures. It is perfectly 

 transparent, and a fihn of it cannot be detected unless tlie surface is scratched." 

 Dr. Mark attaches a small label to the corner of the slide, which serves for the 

 number of the slide and the order of the sections, and at the same time marks the 

 shellac side (otherwise not distinguishable). 



§ The same temperature is used throughout the operation. 



