ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 539 



glycerin or oil, the use of the autoclave is of no special value, since ex- 

 posure to superheated steam acts no more rapidly or effectively than 

 simple heating of those fluids to the same temperature at ordinary atmo- 

 spheric pressure. Heating of spores in glycerin or oil has no greater 

 sterilizing action than simply heating them in dry air at the same 

 temperature for the same period. For the sterilization of these fluids 

 it is necessary to use a temperature of not less than 170° C. for at least 

 half an hour, or 180° C. for not less than ten minutes. The methods 

 commonly in use for the sterihzation of glycerin and similar fluids are 

 quite inadequate to secure sterility with certainty, and accordingly they 

 ought to be abandoned. 



Bacterial Investigation of Liquids. — E. Hesse* discusses certain 

 improvements in his method of studying the l^acterial content of a large 

 bulk of liquid by means of a Berkefeld filter. The fluid to be examined 

 is drawn through the filter by means of a suction pump, and then a few 

 cubic centimetres of water sent in the reverse direction through the 

 filter will wash off the organisms adhering to the outer side of the filter. 

 Thus the bacteria present in a large quantity of fluid, are concentrated 

 into a few cubic centimetres. The author used at first the Berkefeld 

 candle No. 10^, with extra fine pores, but later he used instead a coarser 

 filter, treated with a fine suspension of kieselguhr, or prepared chalk. 

 By means of experiments on guinea-pigs, the author demonstrated the 

 harmlessness of prepared chalk when injected into animals. 



In another place,! the author reviews all the principal methods of 

 bacteriological investigation of water samples by concentration and 

 enriching processes, and gives experimental evidence to show that by 

 the use of a Berkefeld candle impregnated with kieselguhr. 91 p.c. of the 

 organisms present in a large bulk of sample may be recovered in a few 

 cubic centimetres of water, from the surface of the filter. 



Metallography, etc. 



Microstructure of German Silver.J — 0. F. Hudson describes the 

 structure of German silver containing 58 p.c. copper, 18*5 p.c. nickel, 

 23 '5 p.c. zinc ; this alloy consists wholly of the a solid solution. The 

 cold-rolled alloy had a highly distorted structure to which the cores of 

 the casting structure gave a markedly laminated appearance. Specimens 

 were annealed at 700° C. for 1, 10, 24, 48, and 72 hours. The usual 

 growth of crystal took place, and the cored appearance gradually 

 disappeared, though faint traces of coring could be detected in the 

 specimen annealed for 72 hours. The results indicate the extreme 

 slowness of diffusion in this ternary alloy ; diffusion is retarded by the 

 presence of nickel. In a communication to the discussion, H, Garland 



* Centralbl. Bakt., Ite Abt. Orig., Ixx. (1913) pp. 331-4. 



t Arch. f. Hygiene, Ixxx. (1913) pp. 11-28. 



X Journ. Inst. Metals, ix. (1913, 1) pp. 109-19 (14 figs.). 



