ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 681 



or white, in the whole drop is then counted. In making the solutions 

 the authors advocate the use of tabloids, as follows : — 



Sol. A (for lohite count). Sol. B (for red count). 



rr -ui • i (Sodium chloride . "25 grm. m„M„,-.i (Sodium chloride . -25 arm. 



Tabloid | Methyl . violet . -004 grm. Tablold \Eosin .... -0025 gnn. 



Formalin (neutral) "5 c.cm. Formalin (neutral) *5 c.cm. 



Distilled water . 30 c.cm. Distilled water . 30 c.cm. 



White cell count : 5 c.mm. of blood are mixed with 495 c.mm. of 

 solution A and well stirred. This is allowed to stand for about 

 5 minutes. 5 c.mm. of this is taken and blown out on a slide so as to 

 form a drop 'about 10 mm. in diam. This is allowed to dry and is 

 mounted. 



The white cells are stained and easily seen. The actual count is 

 made with £ objective, and the whole drop is gone over in parallel and 

 contiguous lines from field to field. The use of an oblong diaphragm 

 introduced into the eye-piece is recommended for convenience in 

 counting. The count takes from 20-30 minutes. The 1-100 dilution 

 must of course be allowed for in making the final calculation. 



Red cell count : 5 c.mm. of the first (methyl-violet) dilution are 

 mixed with 995 c.mm. of solution B ; 5 c.mm. of this are taken and 

 treated as before. This time however the dilution will be 1-20,000. 



The dilutions may be modified to suit very high or very low blood 

 counts. 



The authors claim for their method permanency of the preparations, 

 and elimination of possible error clue to differences in depth of the cells 

 in ruled counting; chambers. 



'.-> 



Friedberger, E. — Die allgemeinen Methoden in der Bacteriologie. 



Jena (Fischer) 1902, 3 Lief., 397-525 pp., 85 figs. 

 K a m e n, L. — Anleitung zur Durchfiihrung bacteriologischer TJntersuchungen fur 

 klinisch-diagnostische und hygienische Zwecke. 



Wien (Safar) 1903, 8vo, 311 pp., 118 figs., and 12 pis. 



Mez, C. — Mikroskopische Untersuchungen, vorgeschrieben vom Deutschen Arz- 

 neibuch. Leitfaden fiir das mikroskopiscb - pharmakognostische Praktikum an 

 Hochschulen und fiir den Selbstunterricht, 



Berlin (Springer) 1902, 8vo, 153 pp., 153 figs. 



Metallography, &c. 



Chemical Composition of Limestones. Microscopical Methods.*— 

 E. A. Skeats in investigating the mineral character and the changes in 

 the matrix of organisms in limestones, taken from certain upraised coral 

 islands, often found it difficult to distinguish between aragonite and 

 calcite, and occasionally between calcite "and dolomite. For the former 

 purpose he used Meigen's test which depends on the fact that when 

 aragonite is boiled with a solution of cobalt nitrate it is coloured red, 

 whereas calcite is unaffected. The author used the test in the following 

 way : a polished slice of limestone, consisting of coral fragments, 

 gastropods, echinid spines, Halimeda, &c, cemented with a large quantity 



* Bull. Mus. ( omp. Zool. Harvard Coll., xlii. (1903) pp. 65-9. 



