ZOOLOGY AND BOTAXY, MIGROSCOPY, ETC. 105 



Argus with a lieberkiihn has never properly seen the diatom at ail ! 

 This diatom requires tlie liel)erkuhn raised; hnt an AcfiiwcijcJus RaJ;ihsii, 

 a Navkula lyra, and a Triceratlam favus require it to be depressed. 

 A coarse Navkula lyra can be dotted, and the secondaries on a coarse 

 Trkeratium seen with a two-third Heberkiihn, both being balsam mounts. 



B. Technique.* 

 (1) Collecting: Objects, incluiini: Culture Processes. 



New Solid Medium for the Isolation of the Cholera Vibrio.f — 

 H. Gr. Gibson recommends the use of a medium which consists of agar 

 30 grm., pepton 10 grm., starch 10 grm., and sodium bicarbonate 

 l'5grm., litmus, water to 1000 c. cm. ; the starch being added after 

 solution and clarification of the other ingredients and the litmus after 

 sterilization, which should be bv the fractional method. A final 

 reaction of ■ 2 to phelolphthalein should be aimed at. As the cholera 

 vibrio attacks starch with the formation of acid, colonies growing on 

 this medium are distinguished from all others (with the exception of 

 certain diphtheroids and Avater vibrios which also attack starch, though 

 not so rapidly) by acquiring a faint pink colour. Fasces are plated out 

 directly on the medium and a search made for pink colonies at the end 

 of eighteen hours. 



New Culture Medium: '^ Orange Agar." % — R. Dujarric de la 

 Riviere points out that the addition of fruit juices — orange, for example 

 ■ — to agar media favours the orowth of micro-organisms. 125 c.cm. 

 orange juice is added to 75 c.cm. pepton broth (Martin). The 

 mixture is autoclaved at 112° C. for twenty minutes, and is then filtered 

 through Chadrin paper to remove the bulky precipitate that forms. 

 The filtrate is verv clear and of a vellow-gold colour. Agar is added as 

 required to this stock solution in the ordinary manner for the 

 preparation of agar media. Orange agar is acid, but can be rendered 

 alkaline by the addition of soda solution. Alkaline orange agar is a 

 very good medium for the cultivation of bacteria. Bacillus typhosus and 

 B. diphtherise, for example, grow with the greatest ease and give a much 

 more luxuriant growth than is the case Avith controls cultivated upon 

 ordinarv agar. Acid orange agar, on the other hand, lias been found to 

 favour the rapid and abundant growth of various species of fungi either 

 obtained from nature or from artificial cultivations. 



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

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

 (4) Staining and Injecting ; (5) Moimting, including slides, preservative fluids, etc. i; 

 (6) Miscellaneous. 



t Brit. Med. Journ,, ii. (1916) pp. 454-5. 



X C.R Soc. Biol. Paris, Ixxix. (191G) pp. 843-4. 



