In the case of Lawrence v. Barker, 5 Wend. 305, Ch. J. Savage admitted “ there may be cases [on cross-examination] in which great latitude of examination may be permitted, arising from the disposition, temper and conduct of the witnesses, which can be regulated only by the direction of the court, and for which it is difficult to lay down a precise rule.”
Thomas v. David, I Car. & Payne, 350, is a strong authority in favor of the proposition, that in cross-examination, it is legitimate to inquire into the relations which a witness sustains to the party in whose favor he testifies.
Mr. Greenleaf, in his treatise on Evidence, vol. 1, §§ 446-1-8-9, lays down the rule, that on cross-examination, it is lawful to elicit facts showing “the situation of the witness with respect to the parties and to the subject of litigation, his interest, his motives, his inclination and prejudices, his means of obtaining a correct and certain knowledge of the facts to which he bears testimony, the manner in which he has used those means,his powers of discernment, memory and description.” He further adds, that testimony as to collateral facts will be excluded, except on cross-examination. See, also, Cameron v. Montgomery, 13 Serg. & Rawle, 132.
The above rules certainly open a very wide area for exploration. They are, however, well fortified by authority, and, we think, commend themselves to every experienced practitioner. In the very nature of things, much must be left to *565the enlightened discretion of the presiding judge, who, by observing the conduct and demeanor of the witness, is much better qualified than we can be, to prescribe in each case the boundary of collateral facts, within which to restrict the investigation. We will not say that cases may not arise, in which the primary court may transcend the proper limits. We are satisfied, however, that unless the cross- examination seeks to elicit facts which are palpably irrelevant and immaterial, or unless the record affirmatively shows that improper indulgence was granted in the given case, it is our duty to leave the question to the discretion of the presiding judge.
This was an action on a written warranty of the soundness of a slave. The testimony called out against the objection of appellant, consisted of declarations made by the witness, wdio was the auctioneer, while making the sale. These could not be received as evidence of a warranty. All previous negotiations had been merged in the written contract.— Melton v. Watkins, 24 Ala. 436; Gordon v. Phillips, 13 Ala. 567 ; Seay v. Marks, 23 Ala. 532 ; Chapman v. Lathrop, 6 Cowen, 109. Neither was it permissible, in this action on the contract, to give evidence of any fraud practiced in the sale by the vendor or his agent, for the purpose of sustaining the action. If this evidence had been offered on a direct examination, we think it should have been excluded. The question, however, assumes a very different character, when it is called out on cross-examination. It certainly tended to show that the witness, in making the sale, had somewhat connected himself with the question of the soundness of the slave; and we think the proof was allowable, as one circumstance to be considered by the jury in weighing his evidence. See Thomason v. Dill, at the present term.
The question, whether the medical treatise offered in evidence by plaintiff, was proper testimony to go before the jury, has not before been made in this court; nor does it appear to have been much considered, either in England, or in any of the courts oí this country. "Very few adjudged cases can be found in the books ; and those cases are not very satisfactory. Greenleaf, vol. 1, § 440, note 5, is, an authority against the admissibility of the evidence. The only authority he cites to sustain the principle, is Collier v. Simpson, 5 Car. & Payne, *56673. That was a case at nisi-prius, and passed off with little or no examination.
In the case of the Attorney-General v. The Glass Plate Company, 1 Anstr. 39, the question was on the proper construction of, the word “square,” as found in an act of parliament. The court vheld, that the construction of the statute was a question of law,, with which the jury had nothing to do, and hence it was improper to read boohs to the jury to explain this term of art found in the act. The , chief baron, in delivering the opinion of the court, said, that to allow the evidence would be to make the construction “ a question of fact, in place of a question of law.” He proceeded, however, to remark, that a judge “ may well inform himself from dictionaries or books on the particular subject, concerning the iheaning of any word.” It will be seen that this is not an authority against the admissibility of books of science in evidence before the jury.- It simply decided, that the construction of a statute could not properly go before the jury. It is pursuasive to show that books may be consulted on questions affecting any particular art or science.
A question, kindred to this, seems to have been considered in Green v. Aspinwall, 1 City Hall Recorder, 11. We have not had access to the volume referred to, and are indebted for a statement of the principle decided to the Notes to Phillipps on Evidence, (3d edition,) part II, p. 271. In that case, the- question was, the situation of the tide at a given time and place’. Books treating of the subject were admitted, in evidence. This was also á case at nisi-prius.
The case of Harmer’s Lessee v. Morris & Gwynne, 1 McLean, 46, is hot an authority on this point. That was nothing more nor less than the familiar principle of proving a statement previously made by a witness, as having some bearing on his testimony.
The case of Luning v. The State of Wisconsin, 1 Chandler,-178, is a very loose opinion ; holding that it is discretionary with the primary court to receive Or reject medical- or scientific books.-
The case of Bowman v. Woods, 1 Green’s (Iowa) Rep. 441, is an authority on the precisé point we are now considering. In that case the court Say, “ The opinions of an author, as *567contained in his works, we regard as better evidence than the.mere statement .of those opinions by á witness, whc testifies as to his recollection of them from former reading. Is not the latter secondary to the former ?’’ In this case the evidence was held to be competent'.
We think that medical authors, whose books áre admitted or proven to be standard works with that profession, ought to be received in- evidence. Should such works be obscure to the uninitiated, or should they contain technicalities, or phrases not understood by the common public, proper explanation should be offered, lest the jury be thereby misled. That was done in this case. The opinions of physicians, as experts, touching disease and the science of medicine, are, under all the authorities, admissible in evidence. If we lay down a rule which will exclude from the jury all evidence on questions of science and art, except to the extent that the .witness has himself discovered or demonstrated the correctness of what he testifies to, we certainly restrict the inquiry to very narrow limits. The brief period of human life will not allow one man, from actual observation and experience, to- acquire a complete knowledge of the human system, and its diseases. Professional knowledge is, in a great degree, derived from the books of the particular profession! In every step the practitioner takes, he is, perhaps,, somewhat guided by the opinions of his predecessors. His own scientific knowledge' is, from the necessities of the case, materially formed and moulded by the experience and learning of others. Indeed,, much of the knowledge we have upon all subjects, except objects of sense, is derived from books and our associations with men.
It is the boast of this age of advancing civilization, that, aided and facilitated by the printer’s art, the collected learning of past ages has been transmitted to us. Shall we withhold the benefits of this heritage from the' contests of the court-room ? We think not. Evidence drawn from this source being admissible, the question arises, in what form is it to be laid before the jury? Are opinions, derived from the perusal of books, and deposed to by witnesses, safer guides for that body than the books themselves are ?
A principle, familiar to every member of the legal profes*568sion, is strongly illustrative of the propriety of admitting the evidence we are considering. The body of our laws, known as the common law, is generally understood to be unwritten. We prove its existence and its principles by reported cases, and standard elementary writers. With what consideration would an objection be entertained, which on this subject denied the right to consult Coke, Bacon, or Blackstone ? All these weiie elementary writers, and yet they are conceded to be of tiipdiighest authority. If it be objected that the books above named are not laid before the jury for their consideration, but are weighed and expounded by the court, the answer is, that .tljat grows out of the nature of the subject of which they tredt.'- Under our system, questions of law are exclusively, for the court, and with them the jury have nothing to do. All inquiries respecting any other science are questions of fact, for decision by the jury. Can that be a sound rule, which, in the determination of a question involved in one science, allows to the trying body the light shed upon it by the writings of its standard authors, and withholds such lights from controversies inspecting all other sciences ? We think not. — See Attorney-General v. Glass Plate Company, supra ; also, Inge v. Murphy, 10 Ala. 891.
We have recently considered and settled the legal question growing out of the facts, that the sale in this case was made at public auction, on the distinct announcement that no warranty would be given, — that Shelby, the highest bidder, declined to comply with the terms of his purchase, and Williamson, was thereupon, by consent, substituted in his stead as purchaser ; that Williamson, on the next day, and before he received the property of gave his note for the purchase money, required a bill of sale, with warranty of the soundness of the slaves, as a condition precedent to giving his note ; and that thereupon, Stoudenmeier, the executor, executed and delivered to Williamson a bill of sale, with warranty of soundness, and Williamson gave his note, and i’eceived the slaves. In that case, we held that parties, either before or after the consummation of a contract, may either rescind or modify it, and no other consideration is necessary to support such contract of rescission or modification, than the mutual agreement of the parties. — See Thomason v. Dill, at the present term, and authorities cited.
*569In the present ease, Stoudenmeier had the clear right to stand on the terms of his public sale ; and unless he or his agent was guilty of some fraud in the sale, Shelby, on a suit for that purpose, wohld have been adjudged to pay the purchase money. If Williamson agreed to assume Shelby’s responsibility under the purchase, and on the faith of such agreement Stoudenmeier discharged Shelby from responsibility on his bid, then Williamson became bound Ruihe same extent as Shelby was before him. Stoudenme^CT^s^Hlly authorized to disregard Williamson’s demsjjaa o^frarrsCnyy. and commence his suit either against Shelly o£Willi^^on7|| as the agreement of the latter had or jpdt^ot Txfejught^? j release of the former from his contract. fiÍEfe rej&ird shg^r^^ that Stoudenmeier waived this right, anMMe an<^Wi^ liamson, by agreement on the day succeeding t&^daQC&p^lonc sale, so far modified their contract, as to gewn»««to' him (Williamson) a title to the slaves with warranty of soundness. The authorities above cited show that such agreement is upon sufficient consideration, and will be upheld. — Whiteside v. Jennings, 19 Ala. 184.
That a personal representative, in making sale of the effects of a deceased person, may make a warranty, and thus bind himself personally, is settled in this State. — Craddock v. Stewart, 6 Ala. 77.
This view disposes of all the questions raised, either in the evidence or the charge of the court, on the consideration of the bill of sale.
The only remaining question is that in reference to interest. We hold that, ii^this State, whenever one party has a legal right to recover óf another a debt or damages as due at a particular time, he is also entitled to interest as an incident, from the maturity of the demand until the trial, unless some rule of law declare otherwise. — Marshall v. Wood, 16 Ala. 806 ; Foster v. Rodgers, 27 Ala. 602 ; Weaver v. Puryear, 11 Ala. 941. “ The rule in this court,” says Justice G-oldthwaite, in-the case of Rowland v. Shelton, “as to a warranty of soundness, is, that when a slave, from disease, is worth nothing, the purchaser is entitled to recover Ihc actual value of the slave at the time of the purchase, with interest, and such other damages,” &c. — 25 Ala. 217 ; Willis *570v. Dudley, 10 Ala. 938 ; Caldwell v. Sawyer, at the present term.
There is no error in the record, and the judgment is affirmed.