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 carrier 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. ' ' ^"^ 



Where a physician, testifying with regard to a 

 broken leg, has minutely described the nature of 

 the fracture, he may oive 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.59 



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. 



