142 ESSENTIALS OF VETERINARY LAW 
spread by the overflowing of pastures by streams 
which received the discharge of tanneries in which 
infected hides had been treated.27_ Reasonable 
quarantine there might therefore include the pro- 
hibition of the use of such pastures. Dourine was 
formerly supposed to be spread only by inter- 
course, and under such conditions quarantine 
would only prevent such relations between the 
healthy and the sick. The experiments on the 
Canal Zone, however, showed that the disease may 
be spread by flies. A reasonable quarantine of 
many animal diseases must include screening 
against insects. All that is necessary and efficient 
will be sustained; nothing in excess of that would 
be approved by the courts, in most instances; but 
in deciding what shall, and what shall not, be sus- 
tained the courts will be guided not only by past 
usage, but also by scientific advances when 
properly presented. It is necessary that the 
officer presenting some new method for the con- 
sideration of the court remember that his own 
bare statement of fact may not be enough; he 
may be obliged to say how his position in opin- 
ion has been gained. It may not be enough to say 
that yellow fever is only transmitted by the bite 
of the stegomyia, but the officer should state how 
that fact has been demonstrated; and the necessity 
for such presentation is in direct ratio to the new- 
ness of the demonstration. 
A state statute in Wyoming directed the state 
veterinarian to quarantine for certain diseases; 
and it further gave him authority to order infected 
27 Ravenel, Rept. Am. Pub. _ sell, Rept. Wis. Agr. Expt. Sta- 
Health Assn., 1898, p. 302; Rus- tion, 1900, p. 171. 
