This is an appeal by defendant Harry Semler, a dentist, in a malpractice case, from a judgment after verdict assessing damages against him in the sum of $75,000. At the conclusion of the taking of testimony, defendant, by timely motions, moved for a directed verdict, and, after judgment, for a judgment notwithstanding the verdict, or, in the alternative, for a new trial, on the grounds that as a matter of law the evidence failed to show any negligence on the part of defendant which was the proximate cause of plaintiff’s injuries, which motions were denied by the trial court. On the appeal, it is again urged that there is no substantial evidence of negligence or proximate cause warranting the submission of the case to the Wry.
It is alleged in plaintiff’s second amended complaint that defendant was negligent in the following particulars:
“Defendants failed to take the necessary and reasonable precautions immediately after the extraction of plaintiff’s teeth to avoid foreign sub*605stances entering and passing down plaintiff’s throat and trachea.
“Defendants failed, refused and neglected to secure any medical or dental or any other kind of post operative assistance or aid or counsel for plaintiff after being advised of her complaints, pains and symptoms as aforealleged.
“On or about July 19,1948 plaintiff advised defendants that she was having repeated and violent coughing spells, that during said time she was discharging from her mouth a foul, greenish, bile-like substance, that she was unable to sleep at night because of said coughing spells and the discharging of said substance, that she was unable to keep food on her stomach except milk and anacin, and that she felt in a generally weakened physical condition, at which time defendants negligently led plaintiff to believe that her symptoms, pain, and sufferings complained of as aforesaid were commonly associated with the after effects of extractions.”;
that as the proximate result of such negligence, plaintiff alleges that she suffered certain injuries, including an abscessed lung, which necessitated several operations, the removal of several ribs, and the placing of drainage tubes in her back to expel the purulent matter, whereby she sustained permanent injury.-
The evidence discloses that plaintiff, suffering from pyorrhea over a number of years, went to defendant’s office on the morning of July 10, 1948, to have her remaining 17 teeth extracted. A general anesthetic was administered to her, whereupon her teeth were extracted and false ones inserted. Oxygen was administered to her to bring her out of her coma, whereupon she was walked to an adjoining recovery room and placed on a cot. Thereafter Nurse Magner, according to the testimony of plaintiff’s husband, went to the waiting room to summon him to the door of the recovery *606room, whereupon he entered and the nurse left; He testified that when he first saw plaintiff she was lying prone on her back with her head turned to the right. He tried to revive her by shaking her shoulder but there was no response. After remaining in the recovery room for a period of about five minutes, plaintiff regained consciousness. A nurse then brought in a card of instructions for care and a bottle of mouthwash. Plaintiff was asked to return on Monday, July 12, for examination, which she did. At that time a nurse removed her plates and asked her to rinse out her mouth, after which she was examined by Doctor Burton,- who told her that everything was “fine”, and she was asked to return to the office in a week.
Late that night or early the next morning, she commenced getting a “funny sensation” with choking, coughing and vomiting. This condition continued for the following week. She felt very weak, was unable to sleep and had no appetite. She was only able to retain milk and took many anacin tablets as these had been recommended on the instruction card in case she felt the need for medication.
Upon the following Monday, July 19, she returned to the defendant’s office to have the sutures removed. A Nurse Schamel performed this act, and plaintiff informed her that she had been “terribly ill” all week, describing her symptoms. The nurse assured her that “that was the natural thing after the extraction of teeth.” On August 2, she again returned to the dental office but only to make a payment and did not talle to anyone about her condition.
Plaintiff testified that her physical condition became worse and that she went to Doctor Tuhy, who, on October 28, 1948, operated, removed a part of one *607rib and found an abscess of the right lung. She was hospitalized 11 days after this operation, and around the first part of December underwent another operation for the removal of another abscess.
Turning to the alleged negligence of defendant, it is plaintiff’s theory, on the first allegation of negligence, that the defendant was negligent in placing plaintiff on her back rather than on her side on the cot following the extraction of her teeth, she being in an unconscious condition, thereby causing foreign material to pass down her trachea which resulted in the lung abscesses. It is claimed that such a procedure was improper and not in conformity with the rules of the practices of the profession. Plaintiff called as a witness a qualified dentist, Kenneth E. McIntyre, who testified as follows in answer to hypothetical questions:
“Now Doctor, assuming that on or about July 10, 1948 Mrs. Wintersteen went to have 17 of her teeth extracted and that 12 of these teeth were upper teeth and five of them were lower teeth, and assuming that she had a pyorrheatie condition of the mouth and that her teeth had deposits of tarter around and between them, and that about eleven A. M. or so on that day she was administered a general anasthetic, and that about fifteen minutes or so thereafter her husband, Mr. Wintersteen, was taken into a room where Mrs. Wintersteen was lying and that he found Mrs. Wintersteen lying on a cot, that she was lying on her back with her head tilted to the right, that she was in a horizontal position, in other words, and that he observed her eyes and that her eyes were closed, and that he tallced to her and that there was on [sic] response, and that he shook her and there was no response, and that he watched over her while she was lying in this horizontal position with her head tilted to the right for a matter of five or more minutes, after *608which time she awoke. I will ask you, Doctor, under these circumstances whether or not you would say that the ordinary care, skill, and diligence used by the average, ordinary dentist under like circumstances in the locality had been used.
* * *
“A. In my opinion the patient shouldn’t have been in a horizontal position on her back.
Q. Doctor, state what under those circumstances, that is, with reference to her position, the ordinary skill, diligence, and care used by the average, ordinary dentist under like circumstances in this locality would have dictated.
“A. The patient is usually placed on the side so that everything can drain out of the mouth.”
We are of the opinion that Doctor McIntyre’s testimony would be substantial evidence tending to show that the placing of a patient on the back and not on the side would not be in accord with the proper treatment that is ordinarily employed by members of the dental profession of good standing in the same locality. The law requires of a dentist in treating a patient that he exercise that degree of care, skill, diligence and knowledge which is ordinarily possessed by the average of the members of the profession of good standing in similar localities. Malila v. Meacham, 187 Or 330, 335, 211 P2d 747; Darling v. Semler, 145 Or 259, 264, 27 P2d 886.
We have carefully searched the record and are unable to find any evidence from which the jury could find that the plaintiff was placed on her back when put on the cot. The only evidence touching on this question is that supplied by plaintiff’s husband who testified that, after the nurse had come to the waiting room to invite him to the recovery room, he went into that room and found plaintiff on her back with her *609head tilted to the right. Since proper practice would dictate that the patient should be placed on her side, the presumption would be that defendant did place plaintiff in that position when she was laid on the cot. This presumption was fortified by the testimony of Doctor Burton and Nurse Magner who testified that, although they had no recollection of the particulars of who placed plaintiff on the cot or of in what position she was placed, the ordinary practice which they followed was to place a patient on her side with an emissis basin under her mouth for drainage, and that a patient afterward often turned over onto her back in attempting to get into the most comfortable position, which is in harmony with the well-recognized fact that even a person in deep sleep will do this.
In passing, it is interesting to note that plaintiff’s evidence discloses that, although she was lying horizontally on her back, her head was tipped to the right. In this connection, Doctor Tuhy, plaintiff’s witness, testified as follows in answering questions propounded:
“Q. * * * After such an operation with the material coming out so- fast, if she is unconscious the probabilities of it being aspirated are just as great in one position as another if she has her head on the right?
“A. I understood you to say—you asked me whether the probabilities are the same if she were lying on her side with her head tipped over as compared to lying on her back with her head tipped over. I would say there was less likelihood in lying on her side.
“Q. Yes, but you are getting into probabilities of conjecture there, isn’t that right?
“A. No; from gravity the probabilities of secretion are much more likely with the head tipped over. ’ ’
*610Since plaintiff’s head was tipped to the right, it is difficult to understand, as a practical matter, what difference it would make what position her body was in since, in both instances, her head would be tipped over to the right, thus permitting drainage, or “secretion”, as Doctor Tuhy termed it.
We are of the opinion that plaintiff has failed to sustain the allegations of negligence hereinbefore discussed.
Since this case is of unusual importance, we will assume, for the purpose of a discussion of proximate cause, that plaintiff’s allegation of negligence in the foregoing respect was supported by substantial evidence which warranted the submission of the same to the jury. Proximate cause will then next become the pivotal question. In this connection plaintiff asserts that her being placed on her back following the extraction in the manner aforementioned was responsible for foreign matters draining down through her windpipe into her lungs, thus causing the abscesses in her right lung.
When Doctor Tuhy, plaintiff’s witness, was asked the hypothetical question of whether or not he had an opinion that the lung abscesses were connected with or resulted from plaintiff’s teeth extractions, he replied that he thought they were due to the aspiration of the infected material during or after the extraction when she was unconscious from the anesthesia, but that it was more probable that it had happened afterward while she was on the cot, if the dentist had used all the proper precautions during the extraction. When he was asked if he thought it was because of her being on her back on the cot following the extraction that the *611abscesses were caused, he replied that the prone position under general anesthesia in tonsillectomies was one of the least desirable positions to be in since the infected material could drain down into the trachea, and also the coughing and expectorating so soon (two days) after the extractions under anesthesia caused him to think that she had aspirated infected material while on the cot. He also admitted on cross-examination that on account of her pyorrheatic condition it was possible that the infected material could have been aspirated during deep sleep, with or without an operation or the giving of an anesthetic, or that embolism might have occurred from the blood stream during the extractions, or without them, which could have caused the infection to travel via the heart into the lungs, or that it could have happened while she was being transferred to the recovery room after the extraction.
Throughout his testimony Doctor Tuhy insisted that the probabilities were that plaintiff aspirated the foreign material while reposing on her back following the extraction, and that the aspiration in the other particulars were mere possibilities. He concluded:
“Q. * * * in fact you are in .accordance regarding these abscesses, Doctor, that you don’t know the causes at all, you can’t determine them at all. Isn’t that right?
“A. That is true.”
Before proceeding to analyze Doctor Tuhy’s testimony, we call attention to the fact that there was no direct evidence that any foreign substance went down plaintiff’s trachea into her lungs, or that such foreign material was infectious, or that such foreign matter infected plaintiff’s lung to the extent of causing plaintiff’s abscesses.
*612The purport of Doctor Tuhy’s testimony in answer to hypothetical questions was that when he operated in October he found that plaintiff had an abscess in her lung, and that, since she was on her back in an unconscious condition for five minutes after her teeth were extracted, she having pyorrhea, infected material in all probability was aspirated through her windpipe into her lungs, and that such infected material caused the abscesses. As against this supposition or inference, we have his testimony that there could have been aspirations into her lungs while her teeth were being extracted, while she was being taken into the recovery room after the extraction, during the night while she was asleep, with or without teeth extraction, or through pyorrheatic infection getting into the blood stream and finally lodging in her lungs.
The legal question is whether or not, in view of the foregoing testimony of Doctor Tuhy, the proximate cause of the abscess was the placing of plaintiff on her back on the cot in an unconscious condition following the extraction of her teeth.
It is defendant’s position that the plaintiff’s entire case of proximate cause is predicated upon an inference on an inference, arid that this violates § 2-402, OCLA, which, in part, reads as follows: “An inference is a deduction which the reason of the jury makes from the facts proved, * *
It is urged that the only established fact or the fact proved was that plaintiff had an abscess, and that to arrive at the conclusion that such abscess was caused by plaintiff’s position on her back, the following inferences must be indulged in: (1) that foreign matter got into plaintiff’s trachea; (2) that such matter proceeded into plaintiff’s lungs; (3) that such matter was *613infectious, and (4) that such infectious material caused the abscess.
In the case of McKay v. State Ind. Acc. Com., 161 Or 191, 195, 198, 201, 87 P2d 202, may be found a full and complete discussion of an inference upon an inference, with citations of earlier Oregon cases. It was claimed that the decedent received an electric shock while using a telephone. He proceeded to his home in an automobile, and, after traveling about 28 miles, his car left the pavement, throwing McKay to the pavement and causing his death. It was the theory of the plaintiff that McKay’s death was due to heart failure which was caused by the electric shock which he had received earlier that day. Two doctors testified that in their opinion “heart fibrillation, induced by electric shock, was the probable cause of his death.”, which caused him to either die or collapse at the wheel, thus causing his loss of control of the automobile. Speaking through Mr. Justice Lusk, we said:
“But we are of the opinion that the evidence fails to establish that the cause of McKay’s death was electric shock. On the contrary, the question is left wholly in a state of uncertainty.
((* # # * *
“The testimony of Dr. Erwin and Dr. Coe that McKay’s death was due to an injury to his heart has only one possible basis, and that is the fact that the man died. Without that there is no evidence whatever from which such injury can be found, and the doctors did not claim that there is. All that could be definitely known about the decedent was that he had received an electric shock and that he died in an automobile accident a few hours later. But the cause of death was the question at issue, and in whatever form of language the experts might choose to clothe their opinions they necessarily arrived at *614them by assuming as a fact the very thing that was in dispute. In other words, they reasoned that because McKay sustained an electric shock he came to his death, and because he died the electric shock must have produced an injury to his heart capable of causing death or a collapse. This is not reasoning from cause to effect; it is reasoning in a circle.”
We further said that there is sometimes no accountability for automobiles leaving the highway. The drivers of automobiles sometimes fall asleep at the wheel, sometimes there are mechanical defects which cause accidents, and that,
“It could as well be said that, as between two possible causes of decedent’s death, no evidence has been produced which makes one cause appear as more probable than the other, or enables the triers of the facts to do other than guess at the solution of the mystery. In that situation the plaintiff necessarily must fail.” See Annereau v. Ewauna Box Co., 176 Or 509, 159 P2d 215; Parker v. Pettit, 171 Or 481, 138 P2d 592; Vale v. State Ind. Acc. Com., 160 Or 569, 86 P2d 956.
So, in the instant case the only known or proved fact is that plaintiff had an abscess, and, to arrive at the conclusion that such abscess was caused by the improper position of plaintiff on her back, Doctor Tuhy had to indulge in the several inferences hereinbefore set out. It is well known that a person may suffer an abscess from various causes, and to say that plaintiff’s abscess was caused in the manner delineated by Doctor Tuhy would be pure conjecture and highly speculative.
In the case of Spain v. Oregon-Washington R. & N. Co., 78 Or 355, 153 P 470, Ann Cas 1917E, 1104, speaking through Mr. Justice McBride, we said:
“ * * * When the evidence leaves the case in such a situation that the jury will be required to *615speculate and guess which of several possible causes occasioned the injury, that part of the case should be withdrawn from their consideration.”
Plaintiff relies on Clemens v. Smith, 170 Or 400, 134 P2d 424. In that case defendant Smith, a physician and surgeon, was charged with malpractice while removing a cyst from the back of plaintiff’s wrist by failing to use sterile instruments, to the end that plaintiff’s wrist became infected. The evidence showed that the instruments used by Doctor Smith were unsterile, that no infection could come from the cyst in and of itself, and that the infection the plaintiff had came from the kind of germ that could come from unsterile instruments. The facts in the Clemens case are a far cry from the facts in the present case.
In citing the Clemens case plaintiff quoted from Lippold v. Kidd, 126 Or 160, 269 P 210, 59 ALR 875, as follows:
“ ‘ “The law does not demand of a plaintiff that he establish with certainty the proximate cause of his injury. If the proof shows that a certain factor probably bore to injury the relationship of cause, the law is satisfied and denominates it the proximately [sic] cause.” ’ ”
In the Lippold case there were four uncertainties as to the cause of the loss of an eye, and, in denying plaintiff recovery, at p. 170 we said:
“* * * And this court has on previous occasions ennunciated the rule that when an alleged injury may have been due to one of several causes, any one of which may have been the sole proximate cause, there can be no recovery unless it is shown that as between the two or more causes in question, it was the negligence of the defendant which caused the injury.”
*616We will treat plainitff’s second and third allegations of negligence together as they emanate from the same circumstances. They follow:
“Defendants failed, refused and neglected to secure any medical or dental or any other kind of post operative assistance or aid or counsel for plaintiff after being advised of her complaints, pains and symptoms as aforealleged.
“On or about July 19,1948, plaintiff advised defendants that she was having repeated and violent coughing spells, that during said time she was discharging from her mouth a foul, greenish, bile-like substance, that she was unable to sleep at night because of said coughing spells and the discharging of said substance, that she was unable to keep food on her stomach except milk and anaein, and that symptoms, pain, and sufferings complained of as aforesaid were commonly associated with the aftereffects of extractions.”
In connection with the above, plaintiff testified that she told the nurse when she went back on July 19,1948, to have her sutures removed that, “ ‘I don’t know what is the matter with me; * * * I have been having violent coughing spells and coughing up this greenish bile-like substance and I felt as though I was losing weight. ’ ’ ’ Upon being queried, “Did she respond to that?”, plaintiff replied, ‘ ‘ She [the nurse] said that was the natural thing after the extraction of teeth.........”
Since the evidence showed that it was the duty of the nurse to notify defendant of any complaints the patients might make, we will assume for the purpose of this discussion that defendant had knowledge of the complaints of plaintiff which she conveyed to the nurse. There was evidence by Doctor McIntyre that proper practice would dictate that defendant upon being apprised of plaintiff’s condition should have referred her *617“to a physician and have a checkup.” The complaint did not allege that by reason of the failure of the defendant to advise her to go to a physician she refrained from taking such course, nor that had she seen a physician her condition would have been alleviated.
The rule of pleading in the above respect is laid down in Horn v. National Hospital Association, 169 Or 654, 670, 131 P2d 455, wherein, speaking through Mr. Justice Brand, we said:
“The alleged negligence is the failure to diagnose and advise plaintiff concerning her physical condition and particularly concerning her diseased gall bladder. It is to this failure therefore that the chain of proximate causation must be linked. Unlike cases in which affirmative injury is done in the very course of operating upon a patient, the mere failure here to diagnose and advise, in and of itself, caused no damage. Resulting damage could be made to appear only by showing other circumstances which rendered the failure harmful. The plaintiff, in recognition of this fact, was required to and did plead that the undiscovered chronic gall bladder condition was one ‘for which immediate medical and surgical treatment was indicated.’ The next step was to plead that the immediate treatment indicated as necessary would have been administered if the condition had been discovered. This, also, the plaintiff alleged in substance by pleading that, ‘Plaintiff, being ignorant of the nature of said condition, did not at that time obtain any medical or surgical treatment for the same.’ (Italics ours.) The last necessary element in the chain of causation is that the absence of medical or surgical treatment at the time resulted in damage which would not have occurred if the treatment had been administered. The plaintiff alleges that harm occurred as a result of the nondiscovery of the gall bladder condition, but that allegation can only be true if the non-discovery resulted in the alleged nontreatment. ’ ’*618Krause, Evans £ Korn, and Elam Amstuts, of Portland, for the petition. Easley, Whipple £ McCormick; Phillips, Coughlin, Buell £ Phillips; and Lloyd M. McCormick, all of Portland, contra.
Since plaintiff’s complaint was deficient as hereinbefore pointed out, plaintiff could not recover on said allegation of negligence.
In considering the third allegation that defendant was negligent by reason of the nurse’s telling plaintiff that, “That was the natural thing after the extraction of teeth.”, we find that there is no allegation in the complaint nor any evidence in the record that the symptoms alleged and testified to were not the ordinary and probable consequence of extractions, nor is there any evidence of express or apparent authority in the nurse to give such advice. Mrs. Schamel, the nurse in attendance, was a dental and not a registered nurse. The uncontradicted testimony of Doctor Sender was that when complaints were made by patients to the nurses after teeth extractions, it was their duty to report such complaints to the dentists and not give advice. In fact, Doctor McIntyre testified as follows: “My opinion is the nurse shouldn’t give any advise [sic] at all. She has no qualifications to state those things.”
The judgment of the lower court is reversed with instructions to enter judgment in favor of defendant.