Since an insurer becomes subrogated pro tanto to the rights of the insured against a tortfeasor upon payment to the insured under a fire policy, and cannot recover if the insured could not, where in the course of the trial it appears that the insurer has an interest in the cause of action against the tortfeasor, the trial court must, upon its own motion, stay proceedings and order the insurer made a party. Frederick v. Great Northern R. Co., 207 Wis. 234, 240 N. W. 387, 241 N. W. 363. In Patitucci v. Gerhardt, 206 Wis. 358, 240 N. W. 385, it appeared during the course of the suit for personal injuries that the insurer, under an automobile collision policy, had an interest in the cause of action against the tortfeasor. It was held that the insurer should be made a party. The court said: "When it is further considered that subdivision (4) of section 260.19 requires that a liberal construction be given to the section, to the end that closely related contentions may be disposed of in one action, even though in a strict sense there be two controversies, and when it is further considered that the obligation on the part of the trial court to bring in indispensable parties is one that exists. independently of any motion by either party, it must be apparent that section 260.19 has a larger objective than merely the protection of the parties to the action. It is the apparent intention of the legislature that single controversies shall be determined in one action, for the purpose of promoting expedition and economy in the administration of justice. Since the code has abolished distinctions between actions at law and suits in equity, and since section 260.19 is borrowed from the old rules governing equitable actions, we think it is a fair conclusion that the section was intended to apply to all actions, whether at law or in equity. If the section is to be given application to actions at law, we can think of no more appropriate place to apply it than to a situation where a single cause of Where defendants are sued as joint tortfeasors, those having a single liability may have determined the right of contribution against another defendant under sec. 260.19, Stats., though satisfaction of more than their equitable share of the common liability is necessary to complete the cause of action. Wait v. Pierce, 191 Wis. 202, 209 N. W. 475, 210 N. W. 822. Under statute providing that when defendant will have a right of action against a third person for the amount of the recovery against him the third person may be made a party defendant, a personal injury plaintiff suing a railroad company may have made a party defendant a physician giving allegedly improper treatment for the injury received, though the original defendant would have a right of action against the physician for only a part of the recovery. Fisher v. Milwaukee Elec. Ry. & Light Co., 173 Wis. 57, 180 N. W. 269. Physician, sued for malpractice by an employee who has accepted compensation under the Workmen's Compensation Act from his employer for damages sustained over and above injuries received, or if sued by the employer to recover compensation paid by reason of defendant's malpractice, could move that the employer, in the one case, or the employee, in the other, be brought in so that controversies as to the amount of compensation attributable to malpractice could be disposed of in one action. Lakeside Bridge & Steel Co. v. Pugh, 206 Wis. 62, 238 N. W. 872. Employees of a county are not necessary parties defendant to an action against the county to recover damages caused by their negligent acts. Necedah Mfg. Corp. v. Juneau County, 206 Wis. 316, 237 N. W. 277, 240 N. W. 405. RULE 15 Rule 15. Amended and Supplemental Pleadings. (a) AMENDMENTS. A party may amend his pleading once as a matter of course at any time before a responsive pleading is served or, if the pleading is one to which no responsive pleading is permitted and the action has not been placed upon the trial calendar, he may so amend it at any time within 20 days after it is served. Otherwise a party may amend his pleading only by leave of court or by written consent of the adverse party; and leave shall be freely given when justice so requires. A party shall plead in response to an amended pleading within the time remaining for response to the original pleading or within 10 days after service of the amended pleading, whichever period may be the longer, unless the court otherwise orders. (b) AMENDMENTS TO CONFORM TO THE EVIDENCE. When issues not raised by the pleadings are tried by express or implied consent of the parties, they shall be treated in all respects as if they had been raised in the pleadings. Such amendment of the pleadings as may be necessary to cause them to conform to the evidence and to raise these issues may be made upon motion of any party at any time, even after judgment; but failure so to amend does not affect the result of the trial of these issues. If evidence is objected to at the trial on the ground that it is not within the issues made by the pleadings, the court may allow the pleadings to be amended and shall do so freely when the presentation of the merits of the action will be subserved thereby and the objecting party fails to satisfy the court that the admission of such evidence would prejudice him in maintaining his action or defense upon the merits. The court may grant a continuance to enable the objecting party to meet such evidence. (c) RELATION BACK OF AMENDMENTS. Whenever the claim or defense asserted in the amended pleading arose out of the conduct, transaction, or occurrence set forth or attempted to be set forth in the original pleading, the amendment relates back to the date of the original pleading. (d) SUPPLEMENTAL PLEADINGS. Upon motion of a party the court may, upon reasonable notice and upon such terms as are just, permit him to serve a supplemental pleading setting forth transactions or occurrences or events which have happened since the date of the pleading sought to be supplemented. If the court deems it advisable that the adverse party plead thereto, it shall so order, specifying the time |