394 BACTERIA. 



are made as described in the case of water or cholera organisms. Perhaps, 

 however, the most certain way of obtaining all the organisms that are in 

 any sample of earth is to break it down in liquid gelatine as above 

 described, and then make an Esmarch tube cultivation. It is of course an 

 easy enough matter to take a sample of earth from near the surface, but it 

 is much more difficult to take samples from the deeper layers, which can 

 only be done by means of special boring rods, unless access can be gained 

 to a clean cut surface such as those met with in the making of a drain or 

 other such cutting. As most organisms, however, such as the bacilli of 

 anthrax, malignant oedema and tetanus, and the aerobic putrefactive bacteria 

 are usually found near the surface, and as the deeper layers are so frequently 

 almost entirely free from micro-organisms, just as is the ground water that 

 we find in these deeper layers, this is as a rule a matter of comparatively 

 little importance. 



LITERATURE. 



The following works may be referred to : 

 Authors already mentioned. Fraenkel, Griffiths, Hueppe, 

 Koch, Salomonsen, Tyndall. 



AITKEN. Trans. Roy. Soc., Edin., vol. xv., Feb. 6, 1888 ; 



Proc. Roy. Soc., Edin., vol. xvi., p. 139, 1886. 

 BOLTON. Zeitschr. f. Hygiene, Bd. I., p. 76, 1886. 

 BURDON SANDERSON. Reports on the Intimate Pathology 



of Contagion. 1876. 

 CARNELLEY, HALDANE AND ANDERSON. Phil. Trans., vol. 



CLXXVIII., p. 61, 1887. 

 FRANKLAND. Phil. Trans. Roy. Soc., vol. CLXXVIII., p. 113, 



1887 ; Journ. Chem. Soc., p. 373, 1888 ; Proc. Roy. 



Soc., vol. XL., p. 509, 1886. 

 FRANKLAND AND HART. Proc. Roy. Soc., vol. XLL, p. 446, 



1887. 

 MIGULA. Centralbl. f. Bakt. u. Parasitenk, Bd. vm., No. 12, 



p. 353, 1890. 

 MIQUEL. Annuaire de 1'Observatiore de Montsouris. 1877- 



1890. 



NICOLAIER. Deutsch. Med. Woch., No. 52, 1884. 

 PETRI. Zeitschr. f. Hygiene, vol. in., p. i, 1887. 

 PETRUSCHKY. Centralbl. f. Bakt. u. Parasitenk., Bd. vm., 



No. 20, 1890. 

 PFUHL. Centralbl. t". Bakt. u. Parasitenk., Bd. vm., No. 21, 



1890. 

 SCHMELK. Centralbl. f. Bakt. u. Parasitenk., Bd. iv., No. 7, 



1888, and Bd. VIL, No. 4, 1890. 



