On the Biological Examination of Water and Milk. = 33 
or it is the effect or the concomitant of that particular disease. 
In any case the value of a biological examination is not in 
the least impaired; if the presence of a particular organism is 
demonstrated, the previous existence of the disease, whether 
we look upon the organism as the cause concomitant, or the 
effect of that particular disease, is also demonstrated. 
The special organism or microbe which is considered to be 
the cause of typhoid fever was discovered by Klebs, Eberth, 
and Koch almost simultaneously in 1880. This organism— 
known as Eberth’s bacillus, or the bacillus of typhoid fever 
—is found in the viscera (intestines, Peyer’s patches, spleen, 
mesenteric glands, etc.) of patients who have died of the 
disease, and it is from the spleen that “pure” cultivations of 
the bacillus are most easily obtained. The organism is also 
found in the excreta of typhoid patients, but here it is, as one 
would naturally expect, commingled with a host of other 
micro-organisms, and therefore difficult to isolate. 
When, however, the bacillus has been isolated—by methods 
which I shall describe immediately—it can be cultivated 
artificially in various nutrient media, exhibiting characteristic 
modes of growth visible to the naked eye. These macroscopic, 
or naked-eye, appearances are of such vast diagnostic import- 
ance in connection with the study of micro-organisms, that I 
may be excused for referring briefly to the mode of growth of 
the typhoid germ in two very commonly employed and easily 
prepared media. 
1. Nutrient Gelatine—If a sterilised platinum needle be 
charged with a very minute portion of the organism in 
question, and the needle thrust into a tube containing 
sterilised nutrient gelatine, in the course of a day or two, at a 
temperature of about 65° F., a distinct whitish growth be- 
comes visible along the track of the needle, and shortly after 
rounded or ovoid “ colonies” are found to make their appear- 
ance along the side of the needle track. On the free surface 
of the gelatine a growth also takes place, but the border or 
edge of the growth, instead of being even, as is the case with 
most micro-organisms, assumes sooner or later a somewhat 
sinuous outline. At no time do the colonies ever liquefy the 
gelatine. 
VOL, XI. Cc 
