COMPENSATION 119 
jury must therefore know before hearing his ex- 
pert opinion how he claims his standing, in order 
to know how to estimate his statements. No 
amount of general experience as a veterinarian 
would qualify a person ignorant of bacteriology to 
testify as to an animal disease when bacteriologic 
questions are involved. A horse may be appar- 
ently sound, and yet for years be a earrier of the 
Bacillus mallei, and thus be the cause of the loss 
of much stock. A veterinarian ignorant of bac- 
teriology should not be considered competent to 
testify as an expert in a case brought to recover 
damages for the spread of glanders from that 
horse. ‘‘A physician, called as an expert, cannot 
be allowed to testify as to his opinion whether a 
certain plaster, which he has not examined, was 
poisonous; his opinion being based upon his experi- 
ence, study, and facts personally known to him, all 
of which were not in evidence.’’ °7 
Where a physician, testifying with regard to a 
broken leg, has minutely described the nature of 
the fracture, he may give his opinion as to the posi- 
tion of the leg at the time of the accident, and the 
point from which the blow came.®® An expert 
may give the grounds and reasons of his opinion 
in his examination in chief, as well as the opinion 
itself.5° 
When a medical witness, in an action upon a 
warranty of a horse, had stated that he had read 
57 Burns v. Barenfield, 84 59 Lewiston Steam Mill Co. v. 
Ind. 43. Androscoggin Water Power Co., 
58 Johnson v. Steam Gauge & 78 Me. 274, 4 Atl. 555; Keith v. 
Lantern Co., 146 N. Y. 152, 40 Lothrop, 64 Mass. 453. 
N. E. 773, affirming 72 Hun 
535, 25 N. Y. Sup. 639. 
