ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 713 



the eye is convex, and made out of a minute segment of a spherule, the 

 diameter of which should be two inches; the other is a flat glass: it 

 may also be made out of two convex (glasses), and this is better." 



Book ii. p. 43 : — " The third kind of tube is the Microscope for 

 greatly increasing the size of small objects, as fleas, &c. This consists 

 of two glasses and a tube of one inch (? long) or thereabouts, in which 

 small bodies are placed. One glass, that nearest the eye, is convex (and) 

 ground out of a minute segment of a sphere, the diameter of which is 

 at most equal to two inches ; the lower one near the bottom, on which 

 the things to be looked at are placed, is merely a simple piece o lass 

 flat on both sides. 



" Or Microscopes are made of two convex glasses, reduced to the 

 shape of the tube ; one, which is directed towards the things to be looked 

 at, is highly convex, and should be made from the segment of a small 

 sphere ; the other, which is applied to the eye, is somewhat flatter ; of 

 course the proportion to the things to be seen in it must be carefully 

 considered." 



B. Technique.* 

 CD Collecting- Objects, including- Culture Processes. 



Physical Properties of Gelatin, in reference to its use in Cul- 

 ture Media. f — G. C. Whipple made experiments which show that the 

 character of the gelatin used in culture media has a most important 

 influence upon quantitative and qualitative bacteriological work, and 

 that for different observers to obtain results which may be fairly com- 

 parable, it will be necessary to use culture media made from one and 

 the same lot of gelalin. It will be necessary also to follow a most rigid 

 system in the preparation, sterilisation, and use of nutrient gelatin, in 

 order that its physical condition may be the same in all cases. The 

 chemical characteristics of different gelatins with reference to their use 

 in culture media are not discussed, as investigations in that direction 

 are not completed, but the effect of the physical condition of the culture 

 medium on bacterial growth is pointed out. The viscosity, melting-point, 

 and spissitude (jelly strength) of gelatin solutions are described, and a 

 new form of spissimeter and a new method of stating the results of 

 spissitude measurements are suggested. 



Method of Cultivating Anaerobic Bacteria.!— F. C. Harrison de- 

 scribes a method of growing anaerobes which is a combination of the 

 pyrogallol method and a vacuum. Plates or tubes are placed in a bell- 

 jar with stopcock at the top (fig. 144), and this connected with a vacuum 

 pump. The bell-jar is sealed to the dish with paraffin. Pyrogallic acid 

 is placed on the floor of the dish, and the apparatus shown in fig. 145 is 

 inserted after having been filled with KOH or NaOH. The vacuum 



* 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. 



t Technol. Quart., xv. (1902) pp. 127-60 (14 tigs.). 



X Journ. App. Micr., v. (1902) p. 1974 (2 figs.). 



