A MORE COMPLETE DESCRIPTION OF BACTERIUM TRUTT^E. 
415 
The Brownian movement is more pronounced, and a somewhat doubtful motil- 
ity is suggested. Its behavior in Stoddart’s medium (water, 1,000; gelatin, 5; agar, 
0.5; salt, 0.5; pepton, 1 ) does not give a definite answer to the question of motility, the 
freshly isolated culture spreading scarcely beyond the point of inoculation, while 
cultures long in the laboratory when planted extend beyond the original inoculation, 
yet do not cloud thoroughly this medium. In bouillon, however, a slight but dis- 
tinct clouding of the medium is observed in such cultures. A modification of habit 
in the line of an approach toward motility is suggested by the conduct of the organ- 
ism when newly taken from its host, as compared with that when long habituated to 
artificial media. It is to be remembered that it circulates with the blood of the trout 
which it attacks, and while an active parasite in the living trout probably has little 
use for the power of locomotion. In artificial media the ability of the individual to 
change its own position would be of value. An interesting question of variation on 
media in the possible acquirement of motile powers is raised. 
The crucial character — the presence of flagella — has not been demonstrated. 
Man} r attempts, by various methods, to stain flagella have had negative results, and 
for purposes of classification their absence must be assumed. For this reason and 
because of the morphology in the tissues of its host, which is to be regarded as its 
natural habitat, the organism is placed in the genus Bacterium as limited by Migula. 
Pathogenesis. — It is pathogenic to trout, and particularly the brook trout (Sal- 
velinus fontinalis) , in which the disease first appeared. It has also been isolated from 
the Loch Leven ( Salmo trutta levenensis) in epidemic, and in a few cases from lake 
trout ( Cristivomer namaycush) . It has been found thus far only in domesticated or 
aquarium fish and has not been seen in wild fish from the natural waters. Healthy 
brook trout succumb to the disease in a few days, by direct inoculation, beneath the 
skin, into the peritoneal cavity, or into the orbital cavity, and after a longer time by 
mixing cultures with their food, the organism recoverable in all cases from the heart 
blood. Inoculation into the dorsal lymph sac of a frog of 1 per cent of its body 
weight of a bouillon culture was negative, the frog showing no effects. Trout dead 
of the disease may be eaten, after ordinary cooking, without ill effects. A cat has 
habitually eaten and thriven upon the fresh, uncooked bodies of the dead trout, and 
the organism is probably not pathogenic for any warm-blooded animals. 
Illustrations . — The colored illustration of the pigment in +0.5 agar cultures was 
executed by Mr. A. H. Baldwin. The photomicrographs are due to the kindness of 
Dr. Erwin F. Smith, who made them in the laboratory of plant pathology of the 
United States Department of Agriculture. 
