332 PPOFESSOR JOSEPH LISTER, 
be represented by a slender streak not one eighth of the 
diameter of the Bacillus anthracis, and such as, before the 
introduction of Koch’s method, would have escaped notice 
altogether. Now, this disease is totally distinct from pyzmia, 
being not accompanied with multiple abscesses or embolism; 
and thus it has been shown by Koch that septicemia may 
© ) 
ree 
: 
OO 
exist as a deadly blood disease, caused by the development 
of micro-organisms, equally distinct from pyemia and from 
the chemically toxic effects of septic products. 
On some occasions, as the result of the introduction of 
putrid fluid under the mouse’s skin, Koch found, besides 
septicemia, a local affection of the seat of inoculation, in the 
form of spreading gangrene; and, on investigating the part, 
he discovered in it, exactly corresponding with the extent of 
the local affection, another organism very differently formed 
from that of the septicemia, viz. a micrococcus, consisting 
of minute spherical granules arranged in linear series, like 
strings of exquisitely minute beads, as represented at ¢ in 
> 
the woodcut. Believing that this locally developing or- 
ganism must be the cause of the gangrene, he tried to sepa- 
rate it from the bacillus of the septicaemia, and succeeded 
through an accidental observation of great interest. Having 
till that time employed the house mouse in his experiments, 
he happened to try the inoculation of a field mouse. This 
animal, though so closely allied, proved not susceptible of 
the septicemia. The bacillus of that disease was unable to 
grow in the blood of the field mouse, but the micrococcus of 
the gangrene could develop among its tissues. The new 
organism was thus obtained in an isolated form, and, when 
now inoculated into the house mouse, produced in that 
animal gangrene pure and simple, extending for an inde- 
finite period among its tissues. 
Thus the animal body, which had previously been an 
obscure field of labour in this department, in which the 
