308 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The latter is scarcely necessary for objects that are not very delicate. 

 The colouring succeeds perfectly in this way also. 



Mounting Sections in Series.*^ — Prof. E. Kossmann considers 

 that the paraffin method of Dr. Giesbrecht f is far the best for the 

 preparation of sections in series, and especially indispensable when 

 it is desired to retain iri situ in the completed preparation detached 

 portions (such as embryos in the ovary). The soaking of the object 

 in chloroform, suggested by Giesbrecht, before placing it in paraffin, 

 is especially necessary when dealing with chitinous membranes, which 

 are very impermeable. Prof. Kossmann has found that the complete 

 evaporation of the chloroform is a very tedious operation ; bubbles of 

 chloroform are easily left behind in the cavities of the prepared 

 paraffin mass; and he therefore uses an air-bath instead of the less 

 easily managed water-bath. It is made of sheet-iron with glass 

 sliding doors, and two small horizontal glass shelves. Two openings 

 in the top are for a thermometer and a Kemp-Bunsen gas-regulator 

 for low temperatures. Beneath is a Bunsen burner connected with 

 the regulator. This air-bath is heated day and night, and a constant 

 temperature of 50" C. kept up. On one of the shelves stands the 

 glass vessel with the paraffin mixture. Two kinds of paraffin are used, 

 of 56" and 36° melting power. It is very important, for the success 

 of the sections, to have a mixture corresponding to the temperature of 

 the room. A temperature of 18" requires a mixture of 48° melting 

 point. On hot summer days the hardest kinds of paraffin must be 

 used pure. 



The object, soaked v/ith chloroform, is put into the paraffin bath 

 (without any mixing with chloroform), and left there from a few hours 

 to two or three days, according to its size ; after which it is quite 

 uniformly penetrated with paraffin, even in the smallest cavities. 

 The paraffin mass is poured into moulds of thick tinfoil. 



The second shelf of the air-bath is for the slides. The shellac 

 layer on the slide is brushed over with creosote, according to the old 

 method of Giesbrecht, and Prof. Kossmann finds that no running 

 together of the creosote takes place if the brush is lightly used and 

 the slide slightly warmed. The creosote evaporates in a few minutes 

 in the air-bath whilst the next slide is being filled, without danger of 

 over-heating, and without being exposed to dust or damp deposits. 



Creese's Turntable. — The speciality of this form of turntable 

 (the design of Mr. E. J. E. Creese) is the method by which it is 

 driven. A strong steel spring coil, on being wound up, starts a 

 clockwork train of three cog-wheels. The sleeve of the table is 

 made narrow and grooved, the whole train being arranged to secure 

 750 revolutions of the table for one of the driving-wheel, thus 

 providing sufficient power to admit of speed-regulating appliances. 

 The spring is wound from the top of the box, underneath the hand- 

 rest, and the rotation of the table is stopped by pressing down 

 a small brass bead placed at the side of the box. The slide 



* Zool. Anzeig., vi. (1883) pp. 19-21. 



t See this Joumul, i. (1881) p. 9513, ii. (1882) p. 888. 



