ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 369 



adds a few drops of 2 p.c. cocain solution. In an hour or so the animals 

 are sufficiently anresthetised to be studied under the Microscope. It is 

 necessary to put a thin piece of glass or metal between the cover-slip and 

 slide to prevent the animals from being crushed. 



If it be desired to fix the larvae the best results will be obtained from 

 the use of Rabl's, Eisig's or Mingazzini's fluids. The formula for the 

 last is 2 parts of saturated aqueous solution of sublimate and 1 part of 

 absolute alcohol with the addition of 5 p.c. of glacial acetic acid. 

 Acetic-sublimate (5 p.c. aqueous sublimate with 5 p.c. acetic acid) acts 

 equally well. In these fluids the larvaa may be left several, even 

 24 hours. 



If the preparations turn brown by the action of osmic acid they need 

 not be stained but may at once be dehydrated and then passed through 

 cedar oil (24 hours) to xylol and afterwards mounted in Grubler's 

 neutral balsam. 



For staining the preparations both in toto or in sections haamalum, 

 carmalum, hasmacalcium, Ehrlich's hematoxylin, and safranin were 

 used. If they were to be stained on the slide the sections 5-10 /* thick 

 were stuck on with water, but if already stained they were stuck with 

 steam or by Schallibaum's method. 



(3) Cutting-, including 1 Imbedding and Microtomes. 



Fixing and Imbedding Dense Connective Tissue.* — E. Retterer 

 thus formulates the results of his experience : — Avoid too long immersion 

 in alcohol, and too much heat when pieces are impregnated with paraffin. 

 The procedure which he has found invariably to be successful is as 

 follows. The skin is fixed in Flemming's, Zenker's or Branca's fluid, 

 washed in water and then dehydrated in alcohol (90° for 1 hour and 

 absolute for ^ hour). It is then transferred to xylol (20 minutes), and 

 next to a mixture of xylol and paraffin at 36° (30 minutes at 20°). The 

 object is then placed in a test-tube containing paraffin (melting-point 

 36°) at 40° and submitted to the action of a water pump so as to remove 

 the air. After a quarter of an hour in vacuo the tissue is imbedded in 

 paraffin at 54°. Too great heat is avoided by impregnating with liquid 

 paraffin melted off a solid block placed in a test-tube. This step takes 

 about 10 minutes. 



New Methods of Paraffin Imbedding.! — V. Pranter finds that 

 ligroin and carbon tetrachloride are very suitable solvent agents for 

 paraffin. Ligroin, which is obtained by fractional distillation of American 

 raw petroleum, dissolves more paraffin (melting-point 54°) at room tem- 

 perature than chloroform. Carbon tetrachloride dissolves more paraffin 

 than ligroin or chloroform, but less than carbon sulphide ; it is, however, 

 not poisonous or inflammable like the latter. The objects, which have 

 been fixed in alcohol, are placed in thin cedar oil for 12 hours, after 

 which they are transferred to fresh oil for another 12 hours, by which 

 time they are quite transparent. 



The pieces are next placed in ligroin or carbon tetrachloride for at 



* Journ. Anat. et Phys., xxxix. (1903) p. 19G. 

 t Zeitschr. wiss. Mikr., xix. (liK)3) pp. 329-32. 



