ZOOLOGICAL STATION IN NAPLES. 227 



be slightly bent, and its convex face held over the paraffine with- 

 out pressure, A small brush, slightly flattened, is used for the 

 same purpose in Leipsic. 



VI. — Giesbrecht's Methods. 

 (i) Transferring from Alcohol to a solvent of Paraffine.*— 



To avoid shrinkage in transferring tender objects from alcohol to 

 chloroform or an oil, pour a little absolute alcohol into a small 

 glass tube, place the canular end of a pipette containing the sol- 

 vent below the surface of the alcohol, and allow a few drops to 

 flow from it to the bottom of the tube ; into this tube let fall, by 

 the aid of another pipette, or a small spatula, a few drops of abso- 

 lute alcohol containing the objects to be imbedded. The objects 

 Avill sink through the alcohol, which, being the lighter fluid, has 

 taken a superjacent position, and rest on the upper surface of the 

 fluid expelled from the first pipette. Most of the alcohol may 

 now be removed by a pipette, and the objects left to sink gra- 

 dually into the heavier fluid at the bottom of the tube. In this 

 way the replacement of the alcohol contained in the objects by an 

 oil, or some solvent of paraffine, is much retarded, and thus the 

 danger from shrinkage reduced to a minimum. 



Where chloroform is preferred to creosote or oil of cloves, a 

 little ether {cether sidfoiriacs, C4H5O) should be added, as many 

 objects will not sink in pure chloroform. 



To replace alcohol by a solvent of paraffine, and then by par- 

 affine itself, is an operation which may, in many cases, be readily 

 accomplished by employing any one of the ordinary intermedia, 

 such as oil of cloves, bergamot oil, creosote, turpentine, chloro- 

 form, etc. But with tender objects, particularly those with larger 

 or smaller internal cavities, the process is often attended with 

 great difficulties, and in such cases collapse and shrivelling can 

 only be avoided by giving the most careful attention to every 

 step in the process. 



Dr. Giesbrecht recommends, for difficult cases, chloroform,t as 

 it is one of the best, and at the same time the most volatile 

 solvent of paraffine. 



* Giesbrecht. " Zur Schneide-Technik," in Zoolog. Anzeiger, 1881, No. 92, 



t Butschli (Biolog. Centralblatt, B. i, p. 591) has also recommended chloro- 

 form, entirely overlooking, as it would seem, Dr. Giesbrecht's prior pubhcation. 



