316 SUMMARY OF CURRENT RESEARCHES RELATING TO 



water for twelve hours. 8. Wash in three or four changes of distilled 

 water for a half-hour. 4. Place in pure 1 p.c. nitrate of silver for six 

 days in the dark, at a temperature of about 70° C. Tissues must become 

 reddish brown in colour. If they become yellowish-brown, throw away. 

 5. Place in a solution of silver nitrate freshly prepared as follows : 

 20 c.cm. of 1 p.c. silver nitrate. Add two drops of 40 p.c. caustic soda 

 to form a grey precipitate. Then add twenty to thirty drops of strong 

 ammonia, enough to dissolve the precipitate while stirring. Allow to 

 remain at least forty-five minutes. 6. Wash quickly in two baths of 

 distilled water and quickly place in distilled water to every 20 c.cm. of 

 which five drops of glacial acetic acid have been added. Leave in this 

 five to fifteen minutes or until the reddish-brown becomes yellowish- 

 brown. 7. Wash quickly and place over-night in 1 p.c. hydroquinone 

 containing 5 p.c. neutral formol. 8. Wash quickly in distilled water, 

 run up through alcohols rapidly and embed in paraffin through benzole 

 or chloroform. 9. Cut sections and fix on slide. Dry well, then paint 

 slides with 0'5 p.c. celloidin. This is followed by absolute alcohol- 

 xylol, and absolute alcohol-xylol again. Then absolute alcohol to 95 p.c. 

 alcohol down to water (distilled). 10. Then one to two hours in 

 ' 1 p.c. solution of gold chloride neutralized with lithium carbonate. 

 Grubler and Hollborn's gold chloride should be used (flavum, not 

 fuscum). 11. Einse in distilled water and fix in 5 p.c. hyposulphite 

 of soda for fifteen minutes. Wash in running tap-water for two hours. 

 Then alcohols up to absolute. Then absolute and eosin for a minute. 

 Absolute alcohol, xylol, and mount in neutral balsam. 



(5) Mounting-, including Slides, Preservative Fluids, etc. 



Celluloid Covers for Large Microscopical Slides.* — C. Brookover 

 recommends tissue-celluloid sheets for covering large slides such as are 

 necessary for serial sections of large objects, e.g. advanced embryos. 

 These slides may be quite large, 7x3, and the advantage of tissue- 

 celluloid is that high powers and oil immersion may be used. Tissue- 

 celluloid is obtainable from dealers in photographic supplies. The 

 writer mentions one disadvantage, which is that the celluloid cover has 

 a tendency to squeeze the balsam out at the edges where it curls up. 



Venetian Turpentine as a Cover-glass Cement.f — M. Plaut 

 advocates the use of Venetian turpentine for sealing off botanical pre- 

 parations and for other purposes. The resin (Venezian. terpent. rect.) 

 obtained from Grubler, is placed in a porcelain pan and heated in a sand- 

 bath to remove the terpene. In from 4 to 6 hours the desired con- 

 sistence is attained. The mass is then dissolved in ether and placed in 

 a metal can devised and described by the author. When required for 

 use heat is applied to the can and the contents poured out through the 

 spout. Turpentine prepared as above stated is of a gold yellow hue, 

 strongly refracting, and when cold and solid is not sticky. 



* Trans. Arner. Micr. Soc, xxxiii. (1914) pp. 56-7. 



f Zeitschr. wiss. Mikrosk., xxx. (1914) pp. 476-8 (3 figs.). 



