be delivered to plaintiff, it did not matter whether the cow was weighed at any particular place, or by any particular person; and if the cow was weighed afterwards, as Sherwood testified, such weighing would be a sufficient compliance with the order. If they believed that defendants intended to pass the title by writing, it did not matter whether the cow was weighed before or after suit brought, and the plaintiff would be entitled to recover. . . . The court also charged the jury that it was immaterial whether the cow was with calf or not. . . .

It appears from the record that both parties supposed this cow was barren and would not breed, and she was sold by the pound for an insignificant sum as compared with her real value if a breeder. She was evidently sold and purchased on the relation of her value for beef, unless the plaintiff had learned of her true condition, and concealed such knowledge from the defendants. Before the plaintiff secured the possession of the animal, the defendants learned that she was with calf, and therefore of great value, and undertook to rescind the sale by refusing to deliver her. The question arises whether they had a right to do so. The circuit judge ruled that this fact did not avoid the sale and it made no difference whether she was barren or not. I am of the opinion that the court erred in this holding. I know that this is a close question, and the dividing line between the adjudicated cases is not easily discerned. But it must be considered as well settled that a party who has given an apparent consent to a contract of sale may refuse to execute it, or he may avoid it after it has been completed, if the assent was founded, or the contract made, upon the mistake of a material fact,--such as the subject- matter of the sale, the price, or some collateral fact materially inducing the agreement; and this can be done when the mistake is mutual. . . .

If there is a difference or misapprehension as to the substance of the thing bargained for; if the thing actually delivered or received is different in substance from the thing bargained for, and intended to be sold,--then there is no contract; but if it be only a difference in some quality or accident, even though the mistake may have been the actuating motive to the purchaser or seller, or both of them, yet the contract remains binding. . . .

It seems to me, however, in the case made by this record, that the mistake or misapprehension of the parties went to the whole substance of the agreement. If the cow was a breeder, she was worth at least $750; if barren, she was worth not over $80. The parties would not have made the contract of sale except upon the understanding and belief that she was incapable of breeding, and of no use as a cow. It is true she is now the identical animal that they thought her to be when the contract was made; there is no mistake as to the identity of the creature. Yet the mistake was not of the mere quality of the animal, but went to the very nature of the thing. A barren cow is substantially a different creature than a breeding one. There is as much difference between them for all purposes of use as there is between an ox and a cow that is capable of breeding and giving milk. If the mutual mistake had simply related to the fact whether she was with calf or not for one season, then it might have been a good sale, but the mistake affected the character of the animal for all time, and for its present and ultimate use. She was not in fact the animal, or the kind of animal, the defendants intended to sell or the plaintiff to buy. She was not a barren cow, and, if this fact had been known, there would have been no contract. The mistake affected the substance of the whole consideration, and it must be considered that there was no contract to sell or sale of the cow as she actually was. The thing sold and bought had in fact no existence. She was sold as a beef creature would be sold; she is in fact a breeding cow, and a valuable one. The court should have instructed the jury that if they found that the cow was sold, or contracted to be sold, upon the

3