ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 



137 



single sensitive plate which can be used directly as a lantern slide, 

 or as a negative for ordinary prints. The materials used were typical 

 Hocks which had been seasoned ten, fifteen, or more years. From 

 these thin hand-plane sections were prepared. The sections, about 

 6 in. long by 2 or 3 in. broad, were immersed for 24 hours or more in 

 a mixture of absolute alcohol and glycerin, and were kept flattened out 

 under a glass plate. They were then stained with aqueous solution 

 of Bismarck-brown or orange G. The sections were toned in weak 

 spirit, dehydrated in absolute alcohol, and cleared in oil of cloves ; 

 eventually mounted in balsam. If mounted in glycerin jelly, the 

 sections were passed from alcohol to a mixture of absolute alcohol and 

 glycerin, and then to pure glycerin. 



Thus prepared, the sections are used as negatives for direct con- 

 tact printing with lantern slides. A plate of glass is fitted into an 

 ordinary printing frame, and on this the series of wood-sections is 



Fig. 38. 



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arranged in a thin layer of oil of cloves or of glycerin. In the dark 

 room an ordinary lantern slide is placed in contact with these, and 

 clamped down firmly &o as to expel air-bubbles and keep the surfaces 

 uniformly in contact. The plates were exposed to gas-light, the time 

 varying with the intensity. After exposure the plate was washed in 

 alcohol followed by water, or in water only in the case of glycerin pre- 

 parations. The plates were Ilford and the developer hydroquinon - y 

 better results were obtained with weak or used developer than with a 

 strong solution. 



Antibacterial Action of Acrolein.* — Dr. E. Koch and Dr. G. Fuchs 

 record some experiments with acrolein, which chemically belongs to 

 the class of aldehydes and is therefore related to formaldehyde. The 

 microbes tested were B. jpyocijaneus, B. coli, Staph, pyog. aureus,\ and 



* Centralbl. Bakt. u. Par., 1" Abt., xxvi. (1899) pp. 560-3. 



