ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 137 



eryihrosporus, distinguished by its spores having a reddish sheen, and the 

 production of a greenish pigment without any deliquescence of the gelatin 

 in which it was cultivated. Both these bacteria multiply to an enormous 

 extent in water, the quality of the water and the amount of organic and 

 inorganic substances contained in it appearing to have no effect on the re- 

 production, which is, however, materially promoted by an increase of tem- 

 perature. These bacteria were found in most examples of spring water, 

 and appear to originate chiefly from the surface of the neighbouring soil. 

 These bacteria are not pathogenic. 



The author found, on the ether hand, that pathogenic bacteria, when 

 introduced into spring water, never multiply, but disappear after a time, 

 varying in length according to the species and the temperature. He con- 

 cludes that the quantity of bacteria present in spring water is no guide 

 whatever for the wholesomeness or otherwise of the water for drinking pur- 

 poses, since these are mostly entirely harmless ; and that it is impossible, 

 by chemical analysis, to determine the presence of bacteria in larger or 

 smaller numbers. 



Chemical Composition of Bacillus anthracis.* — Dr. M. Nencki states 

 that analysis of pure spore-material of B. anthracis gives only traces of 

 mycoprotein, the principal ingredient being a proteinaceous substance 

 nearly allied to mucine, soluble only in alkalies, which he calls myco- 

 mucine. The pathogenic properties of the bacillus are not due to the pre- 

 presence of a poisonous alkaloid, but to its direct action in destroying the 

 living protoplasm of the cell. 



Distribution of Micro-organisms in Air.f— The experiments under- 

 taken by Dr. P. F. Frankland were conducted by means of Hesse's method 

 of solid culture media. The apparatus employed consisted of (a) a tube, 

 lined by Koch's gelatin peptone, through which a known volume of air 

 could be drawn, and of (h) circular dishes containing the same substance, 

 and employed to ascertain the number of micro-organisms falling on a 

 given surface during a definite time. The apparatus is described and 

 figured. 



Experiments were made on the roof of the Science Schools, South Ken- 

 sington ; on St. Paul's Cathedral ; in rooms, railway carriages, &c., and in 

 the country. 



Tables are given showing the place, conditions, number of organisms 

 per volume of 10 litres of air, and number falling on a square foot per 

 minute. From these it is found that in cold weather the number of 

 organisms in the air is very much smaller than during summer, even after 

 rain. Thus, at the top of the Science Schools, with snow on the ground, 

 there were only 4 per 10 litres of air ; on a cold, windy day, 433 per square 

 foot fell in a minute. After exceedingly heavy rain, 40 per 10 litres were 

 found to be present in the air. The average of these experiments show 

 35 per 10 litres, or 279 per square foot. 



Of the experiments in the country the average showed 14 per 10 litres 

 and 79 on a square foot per minute. The air in gardens was found to be 

 higher than in the surrounding country. 



Of the experiments in Hyde Park, &c., the number of micro-organisms 

 is intermediate between the above two situations ; on an average there were 

 24 per 10 litres of air, and 85 fell on one square foot per minute. 



From the experiments made at different altitudes on Norwich Cathedral 

 and St, Paul's, the author finds that the number of micro-organisms decreases 



* In Polish, 1884. See Bot. Centralbl., xxvii. (1886) p, 347. 

 t Proc. Koy. Soc, xl. (1886) pp. 509-26 (3 figs.). 



