ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 139 



of growth renders it less capable of withstanding the conditions of experi- 

 ment. Hence the discrepant results of various observers on antiseptic action. 



Reduction of Nitrates by Micro-organisms.* — MM. U. Gayon and 

 G. Dupetit contribute a biological study of certain denitrifying microbes by 

 the method of cultures, an examination of the products and mechanism 

 of the chemical reactions which they provoke, and a discussion of the 

 agricultural application of the phenomena. 



The reduction of nitrates to nitrites is brought about by many different 

 microbes ; but this memoir is devoted especially to an account of two which, 

 in the presence of organic matter, decompose nitrates with production of 

 nitrogen and nitrous oxide. These two microbes were obtained by the 

 authors from sewage ; and they have isolated and studied them by systematic 

 cultures in sterilized liquids under various conditions. 



Bacterium denitrificans a, the more active of the two, is • 4 to • 6 /x, 

 broad by 2-4 fj. long, of feeble refraction, and outlines not clearly visible 

 except in stained preparations. They are in very active motion in liquids 

 containing nitrates, and multiply by fissiparity during the first days of 

 development ; afterwards 1-3 spores form in each individual. B. deni- 

 trificans 13 differs little under the Microscope from the preceding ; it is a 

 little larger and more refractive. These two bacteria are best distinguished 

 by the rate of their development and by the products of their action on 

 nitrates under comparative cultures in the same medium. They are best 

 stained by methyl-violet and by gentianin. A sterilized liquid sown with 

 B. denitrificans a evolved gas after eighteen hours. By exact analyses of 

 the evolved gases, and of the fermented liquids, the authors show that the 

 whole of the nitrogen of the nitrate is evolved as gas, and that the whole 

 of the oxygen of the nitric acid is combined with the carbon of the organic 

 matter to form carbonic anhydride. Organic matter is essential to the re- 

 action ; 1 gram of nitre requires • 148 gram of carbon or • 273 gram of 

 albuminoid matter for its complete decomposition. Denitrification is accom- 

 panied by a very considerable rise of temperature — in meat infusions 5° • 45, 

 and in the artificial medium 10°. The destruction of nitrates by soil 

 observed in Schloesing's experiments is 'explained by the authors as the 

 work of bacteria similar to those with which they experimented. 



Hiippe's Bacteria.! — In this important work the different forms of 

 Schizomycetes, their development, and their relationship to one another, 

 are treated of in great detail. The same species may occur under three 

 different forms, which are, of course, not sharply differentiated from one 

 another, viz. (1) The coccus form, including all isodiametric, spherical, or 

 only slightly elongated ellipsoidal cells; (2) the rod-form, with distinct 

 elongation in one direction ; and (3) the spiral form, spiral rods, which 

 can, however, on superficial observation, be readily seen to be curved 

 rods. He regards the presence of true protoplasmic vibratile cilia as no 

 essential condition for spontaneous movement ; the structures hitherto 

 described under this name probably vary in morphological and physiological 

 value. 



As a classification of " genera " and species of Schizomycetes, Dr. Hiippe 

 proposes the following : — A. Bacteria with formation of endogenous spores : 

 1st genus, CoccaccEe, with subgenera Streptococcus (?) and Leuconostoc(?) ; 

 2nd genus, Bacteriaceae, with subgenera Bacillus and Clostridium; 3rd 



* Station Agron. de Bordeaux, Nancy, 1886. See Journ. Chem. Soc. Lond. — Abstr,, 

 1. (1886) p. 823. 



t Hiippe, F., ' Die Formen d. Bakterien u. ihre Beziehuugen zu d. Gattungen «. 

 Arten,' 1.52 pp. and 24 figs., 8vo, Wiesbaden, 1886. 



