_Some Practical Suggestions as to Conduct of Witnesses on the Stand._—In this preliminary examination, the conduct and demeanor of the witness are of no little importance, because it is then and there that he makes his first impression upon the court and jury. He should be perfectly open and unreserved in stating his means of special information, in explaining what are the limits of his personal experience and the extent of his reading; but, at the same time, it would be well for him to avoid all appearance of self-glorification and all tendency to exaggerate his individual acquirements. Often has it occurred that expert witnesses of undoubted capacity and honesty, who are unfortunately grandiose and self-assertive in their manner, have, however honest and able they might be, lost entirely their weight with the court and jury by undue self-complacency and exaggeration of their personal qualifications, during their preliminary examination. This is a matter requiring tact and judgment and nerve, and should be fully understood between counsel calling him and the witness, before the witness is placed upon the stand. In that event, it will be quite safe for the witness to closely follow the questions of counsel by his answers, and to volunteer little or nothing. If his answers are not full and complete enough, counsel can renew the question in the same or in other form or carry the matter into greater detail. If, on the other hand, his answer is too full or he appears too eager, he may create a prejudice against him which nothing can overthrow, and which the art of counsel upon the other side in cross-examination and in making comments upon his testimony when summing up before the jury, will very effectually use to destroy his weight as an expert.[184] _Scope and Extent of Examination of Expert Witnesses._—Having stated how experts may be summoned and qualified, it remains to consider the scope and extent to which they may be examined.