BACTERIOPHAGE 637 
and were represented only by granules which stained with difficulty, 
except upon the inoculation of relatively large amounts of the watery 
residuum, and then the few colonies which developed soon in turn 
became transparent. The filtrate obtained by washing off the colon- 
ies containing transparent areas filtered through Berkefeld filters, 
diluted one to many thousand, added to normal colonies of the homol- 
ogous micrococcus caused the same development of transparent areas. 
This phenomenon could be passed from culture to culture of the same 
microbe without loss of power. 
In 1917, d'Herelle,^ working independently, found that the feces of 
persons convalescing from infecton with the Shiga type of the dysentery 
bacillus contained a filterable principle, or virus, which when added to 
broth cultures of Shiga bacilli, arrested their development and caused 
their solution. When some of the culture thus lysed was passed 
through a stone filter, the filtrate, even in great dilution, caused solu- 
tion of broth cultures of the Shiga bacillus, or the development of clear 
areas in plate colonies. d'Herelle found that his principle, or virus, 
which he believed to be an ultramicrobe (called by him Bacteriophagum 
intestinale) grew only in the presence of living cultures of homologous 
bacteria, in which it produces an inheritable and transmissible lysis. 
It will be seen that this principle, or virus, may seemingly be separated 
from bacterial cells by filtration, but it has not up to the present at 
least been observed to persist apart from living cells. In these respects 
it agrees with the usual characteristics of filterable viruses in general. 
Since d'Herelle's earlier work (of which an account may be found 
in his Immunity in Natural Infection, 1924') a multitude of studies 
has been reported. Phage^ has been detected in soil, contaminated 
water and sewage, and in the intestines of man and several of the higher 
animals. It may be that phage phenomena will furnish an explanation 
for the otherwise unaccountable freedom of the Ganges River from 
excrementitious bacteria, commented upon by Clemesha^ and others. 
Phage phenomena may be studied by cultivating bacteria from a 
suitable source in broth, and after a suitable period of growth, filtering 
through a Berkefeld filter. Some of the filtrate added to isolated 
colonies of the original kinds of bacteria will induce characteristic 
changes if it is present and potent. From the "diseased" colonies the 
phage may be kept alive by the procedure discussed above. 
Resistance of Phage to Physical and Chemical Agents.— Fluid con- 
taining active phage may be exposed to temperatures ranging from 
70 to 75° C. for some minutes, usually without harm. It is quite 
resistant to alcohol, acetone and chloroform, and 2 per cent carbolic 
1 Compt. rend. Acad. Sci., 1917, 165, 37.3; Compt. rend. Soc. biol., 1918, 81, 1160; 
1919. 82, 1237; 1920, 83, 52, 97, 247. 
2 Translation by Smith. 
' The term "phage" is quite commonly used now in place of the longer word "bacterio- 
phage." 
< Bacteriology of Surface Waters in the Tropics. 
