ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 733 



of the same shape (fig. 204) give very satisfactory results. The troughs 

 are made for slides of the English size, but other patterns are provided 

 for by means of grooved slips which are supplied with the trough. A 

 tight fitting lid is also supplied if required. The trough may be used 

 for staining, as a bath, and as a moist chamber. 



Stain for Neuroglia.* — Dr. Yamagiwa has devised the following 

 modification of Stroebe's method for axis-cylinder, and applies it to 

 the demonstration of neuroglia fibres which are stained red. The tissue 

 is fixed in Miiller's fluid and after-hardened in alcohol. Celloidin 

 sections are then stained with a saturated alcoholic solution of eosin 

 for 12 hours or more, and afterwards with saturated aqueous solution of 

 anilin-blue for 4-6 hours. The sections are then differentiated in 

 alcohol made alkaline by the addition of a few drops of 1 p.c. KHO. 

 The sections are then washed in water and afterwards in weak alcohol, 

 after which they are dehydrated in absolute alcohol, cleared up in 

 oleum origanum, and mounted in balsam. 



6) Miscellaneous. 



Micro-structure of Bronzes.f — Mr. A. E. Outerbridge, jun., con- 

 cludes, as the results of some experiments with various bronzes under 

 the influence of different etching fluids, as well as of similar etching 

 fluids employed for a longer or shorter time : — 



" (1) Variations in treatment of specimens cause variations in the 

 results which may be misleading, and it would, therefore, seem to be 

 desirable that some uniform system should be adopted by all investigators 

 in this field. 



" (2) The rate of cooling of a mass of metal affects the micro- 

 structure, so that two specimens of the same ladle of metal are taken : — 

 one from a small casting quickly cooled, the other from a large casting 

 slowly cooled ; or two photomicrographs taken from different portions 

 of the same specimen may show variations in micro-structure that may 

 lead to error. 



" It is desirable, therefore, that some uniform size of specimens 

 should be selected by micro-metallurgists as a standard with which to 

 make comparisons." 



Mr. Outerbridge is also of opinion that structure is affected by 

 " method and time of etching." 



Herr Heyn, of the Royal Micro-metallurgical Department at 

 Charlottenburg (Prussia), agrees in the main with the former state- 

 ments about the micro-structure varying with the rate of cooling, Ac. ; 

 but denies that it is in any way changed by the character of the etching. 

 By using different etching fluids and marking their effects, the observer 

 is able to acquire a knowledge of the various properties peculiar to the 

 different elements of which the structure of a metal is composed, and 

 thus to form a general idea of the micro-structure as a whole. He thinks 

 that the establishment of standard methods would at present, in many 

 cases, tend to misunderstandings. 



* Virchow Aichiv., clx. (1900) pp. 358-65 (1 pi.). 



t Micr. Bull., Feb. 1900, pp. 2, 3; and Journ. Franklin Institute, Jan. and 

 June 1899. 



Dec. 19th, 1900 3 D 



