232 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 
In the 3 German streams Treplin! believes 3 series of cases to be dis- 
tinguishable: (1) Mostly small fish (up to100 grams), still well nourished, 
with only individual, or without recognizable, indurated patches, and 
which present in the abdominal region, at most, 1 hard tumor. (2) 
Somewhat larger fish (up to 200 grams), which Hee: always show in 
several places on their sides hard, somewhat swollen, patches; also 
tumors similar to those on the smaller fishes, mostly on the abdominal 
region. These fishes already begin to emaciate. (3) Fishes of and 
above the preceding weights, showing on the sides, belly, or back large 
ulcers, mostly lying immediately under the skin. A part of the same 
is already broken up; borders foul and red; interior containing a yellow 
pus. The fishes have emaciated greatly, and die. 
Season, Railliet thinks, appears to have no influence, fish being seen 
dead in midwinter as well as in June, July, and August. 
Pollution of streams Railliet considers a minor factor, saying: 
The diversion into the Meuse of manufactory refuse is often blamed for the existence 
of this condition of affairs, but the investigations of M. Ladague tend to incriminate 
rather the erection of dams at certain points on the river, these structures diminish- 
ing the rapidity of current, in the midst of which the barbel ordinarily lives. 
Treplin' believed that the young barbels receive the germ from 
refuse deposits of industrial establishments (breweries, malt houses, 
tanneries, distilleries, etc.) on the headwater of the Saar and Mosel; 
and, further, that these germs enter by the alimentary canal, passing 
thence into the rest of the body, and first make their exit therefrom 
(via the ulcers) in the second or third year. Herr Hanzo,? on the 
contrary, considers the cloth and paper mills as chiefly responsible, as 
these establishments handle old rags which are, he says, saturated with 
infective material. 
Of the views of Treplin and Hanzo, Ludwig considers that of Treplin 
to have the greater degree of probability. Both, however, he remarks, 
consist only of opinions and probabilities, and further leave out of sight 
other sources of contamination. While no sufficient evidence exists for 
holding pollution of water by different industrial establishments respon- 
sible for barbel myxosporidiosis, an indirect connection between such 
water pollution and the disease is by no means to be entirely rejected. 
It is very easily possible that such pollution may favor myxosporidian 
increase and development, and especially that it may, by injuriously 
affecting the general life conditions, diminish the normal resistive 
power of the fish, thus rendering infection more easy. This view ex- 
plains the fact (fide the fishermen) that the barbels at Bonn recover, 
while they die in the Saar and Mosel, in which latter streams pollution 
inust, on account of the smaller volume of water, affect the fish more 
injuriously. 
M. Braun? places less stress upon fouling of the water, as once 
Av ha Td wie, Tepeeeier. ae Fisch.-Vereins, Bonn, 1888, p. 34. 
2In Ludwig, loc. cit., pp. 34, 35. 
3 Review of Ludwig in Centralbl. f. Bakt. u. Parasitenkde, 1889, v, p. 420. 
