146 ESSENTIALS OF VETERINARY LAW 
horse, and each slide should be so marked as to 
be proper evidence to present in trial of possible 
future action in the case. In such cases the court 
would not be reviewing the diagnosis, but it might 
set the diagnosis aside as a violation of discretion, 
in that the veterinarian had not made use of ap- 
proved methods of diagnosis.** 
109. Jurisdiction in Quarantine. Questions as 
to jurisdiction in quarantine occasionally arise.?4 
First it must be remembered that the authority of 
Congress, and consequently of federal officers and 
employees, is found in the power to regulate inter- 
state and foreign commerce. ‘‘ Disease, pestilence, 
and pauperism are not subjects of commerce, al- 
though among its attendant evils. They are not 
things to be regulated and trafficked in, but to 
be prevented, as far as human foresight or human 
means can guard against them.’’*> Therefore 
‘Congress has not only the right to pass laws reg- 
ulating legitimate commerce among the states and 
with foreign nations, but also it has full power to 
bar from the channels of such commerce illicit and 
harmful articles.’’ °° The federal government thus 
has power under the commerce clause to main- 
tain such inspection and quarantine as may be 
necessary to prevent the introduction of infectious 
diseases or their germs from foreign countries, 
or into one state from another. Ordinarily the 
individual states may do nothing which would 
interfere with the federal control over interstate 
83 PUBLIC HEALTH, 407. Peirce v. New Hampshire, 5 
34 PUBLIC HEALTH, 408. How. 504. 
35 License Cases, Thurlow v. 36 McDermott v. Wisconsin, 
Mass; Fletcher v.Rhode Island; 228 U.S. 115. 
