ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



123 



or inclined. The base-plate is fitted with three levelling screws, r and 

 any of his Microscopes can be adapted. Dark slide for quarter and half 

 plates, focussing screen, and Hooke's key, are supplied with the 

 apparatus. 



Fig. 27. 



Guide to Photomicrographic Apparatus.* — Herr C. Eeichert has 

 issued a guide for the use of photomicrographic apparatus constructed 

 by the firm. Most of the apparatus has been described before, but a 

 modification suggested by von Martenson for low-power photography 

 appears to be new. This consists in placing the principal and accessory 

 parts on separate base-boards. This arrangement is found to be more 

 convenient for examining the specimen, and prevents jarring when the 

 Microscope is bent at an angle. 



The photograms, which include objects as various as micro-organisms, 

 the tarsal joint, and metals, are excellent. 



B. Technique. t 

 CD Collecting- Objects, including' Culture Processes. 



Cultivation Medium for Thermophilous Bacteria. J — Dr. A. Mac- 

 fadyen and Dr. F. E. Blaxall have found in potato-agar a good medium 

 for cultivating thermophilous organisms. Hereon they grew as isolated 

 colonies, remained discrete, and it was possible to obtain readily pure- 

 subcultures. Potato-agar is prepared as follows : Potatoes are steamed, 

 peeled, and pounded. To 100 grm. of potato one litre of water is 

 added, the mass steamed for half an hour, and then filtered. To tho 

 filtrate 2 per cent, of agar is added, and the whole autoclaved for 

 15 minutes. It was found an advantage to add 1 per cent, of sail. 

 After neutralisation with soda and further steaming, the potato-agar is 

 filtered into test-tubes and sterilised once more. This medium, which 

 is practically a carbohydrate soil, is referred to as salt-potato-agar. 



* Vienna, 1899, 13 pp., 6 figs., and 18 photograms. 



t This subdivision contains (1) Collecting Objects, including Culture Pro- 

 cesses ; (2) Preparing Objects ; (3) Cutting, including Imbedding and Microtomes ; 

 (4) Staining and Injecting; (5) Mounting, including slides, preservative fluids, &c. ; 

 (6) Miscellaneous. 



X Trans. Jenuer (late British) Inst. Prev. Med., ser. ii. (1899) pp. 1G4-5. 



