should result, if the question were of his negligence in doing so, in the present state of our knowledge the jury could find without any evidence being adduced that his act was in fact very dangerous. It would no doubt be presumed that the actor knew it; but it is believed that he would be allowed to prove in his defence that he was actually ignorant of the properties of that substance. Of course, if he thought that the can contained not nitro-glycerine but condensed milk, that belief of his would be a part of his situation, and no question would arise as to the teachings of experience about nitro-glycerine.

Supplementary to the above mentioned general principles relating to the standard man test and the nature of the actor's situation, there are certain more special rules, two or three of which will be briefly noticed by way of illustration.

A custom is usually evidence that conduct in accordance with it is reasonable. A custom includes the way of acting of standard men. It may also sometimes tend to show that conduct contrary to it is unreasonable. But the actor's own habitual way of acting is not relevant to the reasonableness of his own conduct, though it may be so on the question of what others may reasonably expect him to do.

If a person is caught in a sudden emergency, which would perturb the judgment of a standard man, and has to act quickly, he may be excused for doing something that would be unreasonable if he had had time for more deliberate action. The emergency is a part of his situation. But he must still act as a standard man would act in such an emergency.18

Ordinarily a person may regulate his conduct on the assumption that others will act rightly and reasonably. But in a particular case this assumption must not be persisted in, when the actor knows facts showing that it will not be true.

In certain cases skill or special knowledge is an element in due care; i. e., it is unreasonable for a person who has not competent knowledge or skill to do certain acts.

The reasonableness or unreasonableness of conduct is an inference from data. The data consist of the conduct in question and the facts of the actor's situation. The existence of the data is a

18 New Orleans, S. L. & C. R. R. Co. v. Burke, 53 Miss. 200 (1876).

question of fact. When the data are disputed, the question of negligence must go to the jury, with proper instructions from the court if necessary. The data being given, the inference of reasonableness or unreasonableness, of due care or negligence, is in its nature one of fact, the data furnishing the minor premise and the major premise being drawn from common experience, whereas in a true inference of law the major premise is a rule of law. Therefore the question is regularly for the jury. But in a perfectly clear case, where it is plain that only one reasonable inference is possible, the court will decide it as law. If no reasonable inference is possible, the court must decide the question against the party who has the burden of proof, usually the party who asserts that the other was negligent, and must not permit the jury to make a decision which would rest upon a mere guess and not upon reasonable inference.

However, a decision by the court that certain conduct was or was not reasonable or negligent becomes a precedent. The circumstances of a case in which such a decision is made may be so peculiar that a similar case will never arise again. If so, the precedent is of no importance as a precedent. But the group of facts may on the other hand be one that may often arise, and the precedent be controlling whenever that happens. In this way, although negligence is regularly in law and always in its own nature a question of fact, a number of positive rules of considerable generality have been evolved, that certain conduct in certain circumstances is or is not negligent per se or as law. When one of those rules applies, the question of negligence is really one of law. Instances of such rules are the rules about looking and listening before crossing a railroad track; the rule that it is not per se negligent to act so as to expose another to temptation to do wrong, though that may be negligent in particular circumstances; the rule that it is negligent to point a gun at another person and pull the trigger, even though the actor believes the gun to be unloaded.

Although duties as to due care do not fall within the intended scope of this article, a few words as to such duties will be added.

A duty to use care is a duty to act or omit with reference to the attainment of a certain end or object, what has been above spoken of as the principal object. The law sets that end before the actor and commands him to direct his conduct towards its attainment,

either by doing acts to accomplish it or by abstaining from acts which will tend to defeat it. But in common-law duties the law specifies only the end, not any particular means to be used. The duty is a generalized one to do whatever is reasonably necessary. The actor chooses for himself, at his peril, what particular acts he will do or abstain from. Therefore, in the case of such a generalized duty, it is error for the court to decide or permit the jury to find that due care required the use of specific means, though such an error may be harmless where those were plainly the only possible means.19 To do so would be to impose a special duty, different from the generalized duty to use care, which the court or jury has no right to do. For instance, although an innkeeper must use due care for his guests' personal safety, it cannot, in the absence of a statute, be laid down as a rule of law that he is negligent in not providing his house with fire escapes.20

When a common-law duty exists to direct conduct towards a certain end, certain particular means are sometimes required by statute. Thus an apothecary ought to use care not to sell poison in circumstances where danger will probably arise from its being mistaken for a harmless medicine. If there is such a danger, he can guard against it in various ways, and under the generalized duty he may choose any of those ways. But a statute may require him to put a particular kind of label on the bottle. So a city may be under a generalized duty to use care to prevent persons from falling into an excavation in the street, which it can perform by taking various precautions. But a statute may specifically require a fence or lights at night.

Such statutes create specialized duties, which in their own nature are not really duties to use care for an end, but are positive peremptory duties to do certain acts precisely described. The object to be attained merely furnishes the reason why such a duty was created; it does not enter at all into the definition of the duty, as does the object when the duty is really to use care. Such duties lie in strictness outside of the law of negligence. But breaches of them are usually called negligence. When the object is also the object of a generalized duty to use care, and the specialized duty in fact

19 McGrath v. New York Cent. & H. R. R. R. Co., 63 N. Y. 522 (1876); Legge v. Tucker, 1 H. & N. 500, 26 L. J. Ex. 71 (1856).

20 Yall v. Snow, 201 Mo. 511, 100 S. W. 1 (1906).

overlaps the generalized duty and merely, in effect, points out a preferable manner of performing it, the action may usually be for a breach of either duty; and if the generalized duty is sued upon, the breach of the specialized one will usually be evidence, sometimes conclusive evidence, of negligence. In such cases there seems to be no very strong objection to classing the specialized duty among duties to use due care and calling its breach negligence. But when there is no generalized duty to use care for a certain object, either no common-law duty at all or the common-law duty is not simply to use care but is a peremptory duty to accomplish the end, such a classification and nomenclature is wrong and confusing. Thus the duty of the keeper of a fierce dog, which he knows to be such, to prevent it from biting another person is not a duty to use care. It is peremptory. If the dog bites any one, the keeper is liable, whether he was negligent or not. On the other hand, dogs not being generally dangerous, if he does not know of the dog's propensity, he is under no duty at all. In either case a statutory duty to muzzle the dog should not be classed as a duty to use care, or letting the dog go at large unmuzzled, as negligence.

There is a negative duty of due care of very great generality, resting upon all persons and owed regularly to all persons, not to do negligent acts, i. e., acts which are unreasonably dangerous to persons or tangible property. There is some conflict of opinion as to whether this duty is owed to persons who are in the situation of trespassers or licensees.

There is no affirmative duty of equal generality, i. e., no general duty to do acts, to take precautions, to prevent injury to others. The general rule is, that a person is not bound to do acts for others' benefit; he may sit still and let things take their course. Affirmative duties to do acts to protect others arise only out of special circumstances in which the actor is placed. Without trying to go into details, to define the duties precisely, or to make an exhaustive enumeration, the most important of those affirmative duties are as follows:

(1) A person who has done or is doing an act that will be unreasonably dangerous unless precautions are taken against the danger, must use due care to take such precautions as reasonableness requires. If the precautions are not taken, then in an action for a tort usually either the doing the act, which would be a breach

of the preceding duty and a malfeasance or misfeasance, or the omission of the precautions, which would be a non-feasance and a breach of this present duty, may be made the ground of complaint. When the precautions ought to be taken at the time of the act, the doing the act without the precautions is often spoken of as doing a lawful act in an improper manner, which is a misfeasance.

(2) A person who delivers a thing to another or furnishes a thing for another's use, comes under duties to use care either not to deliver or furnish a thing which is unreasonably dangerous at all, or, if the thing is dangerous but it is nevertheless not wrong to deliver or furnish it, to take precautions, if reasonableness requires that, against the danger. Often reasonableness will not require any precautions. There is no general rule that it is unreasonably dangerous to deliver or furnish a dangerous thing to or for another even without taking any precautions against the danger. The deliveree or furnishee may understand the nature of the thing and be able to guard himself; or it may be a sufficient performance of the duty to warn him of the danger. In the case of furnishing things for use, there is some conflict of opinion as to what kinds of things are so dangerous as to bring this duty into operation. It is laid down that the thing must be "inherently dangerous." There is also a great and irreconcilable difference of opinion as to who the person is for whose use the thing is deemed to be furnished, and to whom the duty is owed.

(3) In some circumstances a person having a dangerous thing in his possession which is attractive to children or animals, in a place where, led by their natural instincts which they cannot be expected to resist, they will be tempted to meddle with it and so expose themselves to danger, must take reasonable precautions against that. The authorities conflict as to whether this duty applies when the child or animal is a trespasser.

(4) The possessor of a dangerous thing must use due care to prevent it from doing harm. This duty is owed for the protection of persons or things being where they are by virtue of a right. There is no general duty not to keep dangerous things in one's possession, and to do so is not per se negligent. As to some kinds of dangerous things, e. g., dangerous animals and under the old common law fire, there is a peremptory duty to prevent them from doing harm, which is not merely a duty to use care. In some places there is