198 Profs. P. F. Frankland and Marshall Ward. 



body of a sheep and is carried into a stream. In considering this 

 example, the observed facts as to the susceptibility of anthrax to low 

 temperatures should be borne in mind. The great reduction in 

 temperature would alone suffice to impress it with effects very different 

 from those of its previous environment — the tissues of a warm- 

 blooded animal — and matters would be made no simpler by the 

 differences in exposure to the oxygen of the air, the light of the sun, 

 and so forth.* 



That such a view is not without foundation is sufficiently proved 

 by recent researches on the action of heat, light, and oxygen on this 

 very bacillus in question. 



To take the case of temperature first. It is generally agreed that 

 Bacillus anthracis cannot go on growing and dividing below about 

 15° C, nor above about 45° C, and that it thrives best at some 

 temperature near 35° C. ; it is also agreed that it is markedly 

 susceptible to the presence of free oxygen in its normal development. 

 Although undoubtedly favoured by presence of oxygen, the anthrax 

 bacillus will grow in the presence of only a very small quantity of air, 

 (Liborius, ' Zeitschr. f. Hyg.,' 1, p. 170). Under favourable circum- 

 stances, but only if oxygen is present and the temperature fairly 

 high, the bacilli form spores in their interior. This complicates 

 the matter under discussion, for these spores are sometimes capable 

 of remaining uninjured for long periods under conditions which would 

 inevitably kill the vegetative rodlets. 



Now Rouxf has lately shown that in a given culture containing 

 these spores some individuals are more resistant than others, and that 

 when germinating it is of importance to a given spore whether it is 

 near the surface of a liquid or deeper down ; that at high tempera- 

 tures, in contact with free atmospheric oxygen, the virulence of a 

 given culture can be attenuated,]; though no such attenuation results 

 when out of contact with air. 



These are by no means all the facts that have to be regarded, however. 



* Possibly by far the most important of the destructive influences of fresh water 

 on such microbes is that of the change in the conditions of osmosis, which is also 

 entirely substantiated by experiment, and is in harmony with what we know of the 

 physiology of living tissues (see Marshall Ward, " On Some Eelations between Host 

 and Parasite," &c, the Croonian Lecture for 1890, ' Roy. Soc. Proc.,' vol. 47, 

 pp. 393 — 443, and references to the works of Pfeffer and De Vries therein ; also 

 Fischer, " Die Plasmolyse der Bacterien," in £ P»er. ub. d. Verhandl. Sachs. Gresellsch. 

 Wiss. zu Leipzig,' vol. 1, 1891, pp. 52 — 74, and Wladimiroff, " Osmotische Vers, 

 an lebenden Bakterien," in ' Zeits. Physik. Chem.,' vol. 7, pp. 529 — 543). 



f Roux, " De l'Action de la Chaleur et de l'Air sur les Spores de la Bacteridie 

 du Charbon " (' Ann. de l'lnst. Pasteur,' vol. 1, 1887, pp. 392—399). 



J We ought to deal with this subject very cautiously, for others have stated, and 

 some confuted, this previously ; but of course we are not concerned with all the 

 details here. 



