This case comes to us upon the pleadings. The essential questions are whether plaintiff, appellant herein, may invoke the doctrine of res ipsa loquitur in alleging hi$ cause of action, and whom he may join as defendants. • . =

. The petition alleges that on or about August 6,1963, plaintiff entered St. Elizabeth’s Hospital, where he was operated upon by defendant Michael M. Jailer, a physician and surgeon, for the removal of a calcified deposit in the right shoulder joint; that Dr. Jailer was assisted by the other three defendants, Aldoj Bossini, Mary A. Kurtz and Julie Doll, all registered nurses; that when plaintiff went into surgery he had no impairment off the radial or ulnar nerves in the right arm; that following the surgery he was unable to extend certain fingers of his right hand, suffered restriction of movement in his right w;rist, numbness in his right hand, soreness and discomfort in his right hand and wrist, “and that such injuries do not arise in the course of said surgery in the exercise of ordinary care, skill' and diligence”; and that what happened during surgery is unknown to plaintiff due to his anesthetized condition, but “is within the exclusive knowledge of the defendants present in surgery dur-! ing plaintiff’s unconsciousness, as to what happened to cause1 his injury while under their care and control.”

Apparently, service of summons was not obtained on de-. fendant Bossini. Defendant Doll demurred to the petition foi;j failure to state a cause of action against her. Defendant Kurtz; moved to make the petition definite by alleging when and how;, plaintiff claims she assisted defendant Dr. Jailer. Defendant; Jailer moved to make definite in several particulars and tqi strike certain portions of the petition.

The demurrer of defendant Doll and the motion of defend-j ant Kurtz were sustained. The motion of defendant Jailer was; sustained in part, perhaps the most significant being with re-j spect to the striking of the allegation “that.such injuries do not; arise in the course of said surgery in the exercise of ordinary-care, skill and diligence.” Although these .words are in thej form of a legal conclusion, they constitute a necessary- and,, therefore, permissible allegation for invoking the rule of res.i ipsa loquitur, which otherwise could not be stated.

The principle of res ipsa loquitur is well established in! Ohio. It is usually expressed in some such language as that *208 found in the first paragraph: of the syllabus of Schafer v. Wells (1961), 171 Ohio St. 506:

“Res ipsa loquitur, as a rule-of evidence permitting hut not [requiring the jury or, where there is no jury, the trial court to rdraw an inference of negligence, may be applicable in a case where the instrumentality causing the injury is shown to have been within the exclusive management and control of the de-. Jendant and where the circumstances attending the injury were . ¡of such a character as to warrant the conclusion that, in the ¡ ¡ordinary course of events, such injury would not have occurred if ordinary care had been observed. (Paragraph one of the syllabus of Renneckar v. Canton Terminal Restaurant, Inc., 148 Ohio St. 119, and paragraph one of the syllabus of Soltz v. Colony Recreation Center, 151 Ohio St. 503, approved and followed.)”

See, also, Fink v. New York Central Rd. Co. (1944), 144 Ohio St. 1.

Frequently emphasized as being of considerable weight fin determining the applicability of the doctrine is a situation ] where the facts are peculiarly within the knowledge of the defendant. 38 American Jurisprudence 954, Negligence, Section 262.

The cases just cited and many others point out that the 'doctrine of res ipsa loquitur is not a substantive rule of law, ¡but a rule of evidence which permits but does not require the jury to draw an inference of negligence under the conditions presented. It is not surprising, therefore, that the question in most of the cases which have been cited in the briefs and of 'which we have knowledge arises at the trial rather than upon ,the pleadings.

In his petition plaintiff has joined as defendants the nurses .who assisted defendant Dr. Jailer, asserting the right to join principal and agent, under Section 2307.191, Revised Code. It. appears to us that the question is not one of joinder, but rather ; whether the principle of res ipsa loquitur shall apply to one who is not in charge, but only assists the person who is. By the very definition of the doctrine, it cannot be applied to one who is not in control. The person in control will be responsible for any negligence of his agents: bnt in tie circumstances alleged there can *209 he no inference of negligence not pleaded against any of the 1 nurses, who were not in control.

We find no error in the rulings on the motion and demurrer;,, of the two defendant nurses.

It is our opinion that the petition alleges a cause of action against the defendant Jailer. According to the petition, plaintiff placed his life and his health in Dr. Jailer’s hands. The sur-' geon is the one person exclusively in charge in the operating room. While it is true that he cannot insure the success of the operation, yet the exercise of ordinary care requires of him a! high degree of diligence. It must he presumed that he, rather ; than the plaintiff, is charged with knowledge of what occurred1 during surgery. In event of disaster, the rule of res ipsa lo-quitur requires of him an explanation.

Defendants object that plaintiff has not identified the “instrumentality” which caused the harm. In most of the cases, some physical object or substance has been so identified. Plaintiff’s obvious inability to do so here because of his condition should not defeat his claim; rather, it is a striking demonstration of the need of the doctrine if he is not to go remediless.

That the term, “instrumentality, ’ ’ as used in connection with res ipsa loquitur must be accepted in a much broader sense than as a perceptible object is clear from the cases. For ex-, ample, in Soltz v. Colony Recreation Center (1949), 151 Ohio St. 503, Judge Taft, speaking for the court, frequently employs such terms as “agency or occurrence,” “instrumentality or pc-, eurenee,” and the like. Where a defendant is in complete con-,: trol of a procedure which results in injury and he alone has the means of knowing what occurred, it would appear to do violence to the principle behind the rule of res ipsa loquitur to require plaintiff to allege how and by what physical means his injury occurred.

The Supreme Court’s broad interpretation of the word, “instrumentality,” further appears in Oberlin v. Friedman (1965), 5 Ohio St. 2d 1, on page 9.

This Oberlm case was emphasized by appellee Jailer in argument. Paragraph three of the syllabus thereof states:

“Generally, the doctrine of res ipsa loquitur is not applies able in maLpracticg_actiqns in which its .claimed taTjpIkabi]rfeis4 *210 based solely upon tie fact that tie treatment was unsuccessful jor terminated with poor or unfortunate results.”

We do not understand this language to mean tiat in all «circumstances a particular profession enjoys immunity from; ■the application of res ipsa loquitur.

In tiat case, as in most of tie cases cited, tie plaintiff was¡ j given iis day in court, and it was only after ie had presented) j iis evidence tiat tie court decided upon tie applicability of tie1 doctrine to tie facts. It is interesting to note tiat tie defendant, in tiat case was an anesthetist and not tie surgeon. We believe1 tie same consideration should ie given tie plaintiff here.

Tie case of Fowler, a Minor, v. Seaton (1964), 61 Cal. 2d 681, 394 P. 2d 697, cited by plaintiff, while not binding upon this court, furnishes a striking example of tie helplessness of a plaintiff in such a situation as tie present if ie were required to identify tie “instrumentality” and manner of iis injury. Tiat was a case of a small child who was grievously injured while in preschool nursery. Obviously she had suffered a severe blow; to tie head. It would be a denial of tie doctrine to require tiat she allege and prove what struck her and how.

In tie present case, it is our opinion tiat it was error; to require plaintiff to allege when tie operation was claimed to» have been performed, or to state tie manner in which defendant Jailer was assisted by tie nurses. Tie precise nature of plaintiff’s claim was already clearly stated. See Section 2309.34, Be-vised Code. Furthermore, ie alleged tiat ie did not know what ¡occurred during tie operation. It was also erroneous to require ■ him to strike tie averment already quoted, which is a necessary part of a petition invoking tie doctrine of res ipsa loquiturr “tiat such injuries do not arise in tie course of said surgery in tie exercise of ordinary care, skill and diligence.”

We find these errors to have been prejudicial to tie rights; of tie plaintiff.

Tie judgments in favor of tie defendants Doll and Kurtz wiH be affirmed; tiat in favor of defendant Jailer will be reversed, and tie cause remanded to tie Court of Common Pleas for. further proceedings according to law.

Judgement accordingly.