190 MICROSCOPICAL TECHNIQUE, 



growth of diatoms. They increase most rapidly during those 

 seasons of the year when the water is in circulation throughout the 

 vertical currents. During these periods not only is food most 

 abundant, but the vertical currents keep the diatoms near the sur- 

 face, where there is light enough to stimulate their growth, and 

 where there is abundance of air. Some species display strong 

 heliotropism, moving towards the source of light. — Pharm. Journ. 



A New Method of Staining Nervous Tissue.— Vastarini-Cersi 

 (Rif. Med., Feb. 14, 1896) describes a new and effectual method 

 of staining the spinal cord, etc., for macroscopic purposes. The 

 entire cerebro-spinal axis, with the meninges, is plunged into about 

 3 litres of an aqueous solution of formaldehyde (16 per 1000). 

 The tissue is left in the medium for two weeks, the meninges 

 being removed on the second or third day. Sections from 3 to 

 5 cm. thick are then cut and kept in distilled water, or, better, in 

 alcohol at 40°, for twelve or twenty-four hours ; then plunged into 

 75'' solution of AqN03 i^^ the dark. The white substance soon 

 becomes stained brown. A prolonged stay in the Aq NO3 sol. 

 does no harm. The stain may be fixed for an indefinite time if 

 the preparation is left for two or three days in the dark in distilled 

 water and then in alcohol at 70"^. Tissue so prepared shows in 

 the clearest manner the relations between the white and the grey 

 substance. For example, in the medulla one could distinctly see 

 with the naked eye the respiratory fascicules of Krause. The 

 advantages claimed by the author for this method are its simplicity 

 and rapidity of execution, the constancy of the results, and its 

 great teaching value. — Brit. Med. Journ. 



Differentiation of the B. coli from the B. typhi abdominalis.— 



YX^Xi^x (Zeiisch. f. Hyg.^ysXl.) uses plates prepared with Holtz's 

 potato gelatine, to which, after it has been made slightly acid, 

 T per cent, of iodide of potash has been added. Even on this 

 unfavourable medium the B. coli grows freely and quickly, but no 

 colonies of the B. typhi abd. are visible for forty-eight hours, and 

 they appear as extremely fine, small, shining patches, like drops of 

 water. Controlling his experiments by Pfeiffer's immune-serum 

 process, Eisner always obtained positive results from typhoid stools. 

 Piorkowski, at the Berlin Medical Society (June 10, 1896), reported 



