536 SUMMARY OP CUREENT RESEARCHES RELATING TO 



Mounting Fresh-water Algae.* — Mr. L. B. Hall finds a very 

 successful process to be the use of pure glycerin, carbolated. The 

 objects are first placed in a dilute solution of iodine (tinct. iod. 

 2 min.j water 1 oz.) 2-5 minutes, then stained (iodine-green), and put 

 into dilute glycerin (10 per cent.), and gradually transferred to 

 thick glycerin. 



Cultivation of Microbes.f — According to Dr. H. Fol, it is possible 

 to obtain a perfectly sterile liquid by one of four methods, viz. : — 



1. Filtering through some material whose meshes are suflSciently 

 fine to arrest the smallest organisms. The only material really 

 practicable for this purpose is the un glazed porcelain used by Pasteur 

 and Chamberland. 



2. Obtaining the liquid directly from the internal organs of one 

 of the superior animals ; the digestive tract being considered, for this 

 purpose, an external organ. Pasteur's experiments have shown that 

 the tissues of such animals are the most perfect filters known, neither 

 permitting the entrance, nor tolerating the existence, of any foreign 

 material, unless the tissues are diseased. 



3. Sufficiently prolonged exposure to a temperature of at least 

 110° C. This is the lowest necessary for the destruction of spores, 

 although 80° C. is sufficient to kill bacteria in the growing condition. 

 The length of the exposure must not be less than an hour ; the longer 

 the time beyond this, the greater the security. 



4. Intermittent heating, invented by Tyndall, and much used in 

 Germany. This consists in making the spores germinate, in order to 

 kill the full-grown bacteria at 80° C. For this purpose the vessels 

 containing the fluid to be sterilized are kept at 20-30° C. to favour 

 the growth of the spores, and are every day raised to 80° C. for one 

 hour, to destroy such bacteria as have become fully developed. This 

 method takes much time, and its results are always uncertain. 



Of all these methods, the third, that of destroying the germs once 

 for all, is the one giving the greatest security and ease of manipula- 

 tion. It has but one fault, that of coagulating all albuminous 

 substances which can be solidified at the temperature of boiling water. 



Pure Cultivations of Bacterium aceti.| — In order to obtain pure 

 cultivations of B. aceti, Mr. A. J. Brown adopted, as the most suitable 

 method, a combination of Klebs' "fractional" and von Nageli's 

 " dilution " methods. The author describes the appearance presented 

 by the film formed on beer and other solutions. He considers that, 

 besides B. aceti and B. Pasteurianum, there is a third species capable 

 of oxidizing alcohol to acetic acid ; he therefore describes the 

 morphology of B. aceti, and the action upon it of various reagents. 

 He then describes the action of B. aceti upon various substances. It 

 oxidizes ethylic alcohol to acetic acid, and a trace of (probably) 

 succinic acid. In an insufficient quantity of oxygen a trace of a 

 substance resembling aldehyde is formed. When no alcohol is 



* 11th Ann. Eep. Amer. Postal Micr. Club, 1886, pp. 13-4. 

 t La Nature, 1885. See Science, v. (1885) p. 500. 

 X Journ. Chem. Soc. Lond., 1. (1886) pp. 172-87. 



