16 ESSENTIALS OF VETERINARY LAW 
judgment. In official life, ministerial duties are 
exactly prescribed by law; and the officer or em- 
ployee must do all that the law says, in the way 
that it demands, and no more. In discretionary 
positions the officer must decide his own course of 
action to no small degree. When a veterinary sur- 
geon is engaged to look after the condition of 
stock which a man is about to buy, it is to be 
presumed that it is because the employer desires 
the professional judgment of the veterinarian. 
Having employed this veterinarian it would not 
be a fair deal for the surgeon to send someone 
else in his place (unless the substitution were 
previously agreed upon with the employer), and if 
such a substitute be sent the employer would not 
be liable for the payment of the substitute. He 
would not be liable for the fee of the man em- 
ployed, for the man employed did not, in the case 
supposed, perform the duty imposed in the con- 
tract. He would not be obligated to the substi- 
tute for he had no contract, either expressed or 
implied, with him. So where a physician was 
employed to treat the sick of the community, he 
could not collect for the services of a substitute, 
nor could the substitute collect directly.24 It fol- 
lows also that an officer whose duties require the 
use of judgment cannot leave the performance of 
them to a substitute.2° Where the duties are pure- 
ly ministerial, like the writing of a license, the 
duties may be performed by another. 
24 Chapman v. Muskegon Co.. 25 PuBtic HEALTH, 328, 272. 
169 Mich. 10, 134 N. W. 1025; 
Hickman v. MeMorris, 149 Ky. 
1, 147 S. W. 768. 
