[1] Defendant contends the trial judge erroneously admitted into evidence State’s Exhibits 2 and 3. These exhibits were bottles of Singletary Rat Treatment, a rat poison, bought on 14 May 1974 by Edward Jarman, then Sheriff of Anson County, from the same drugstore where on 31 August 1973 defendant had allegedly bought the same type of rat poison. Defendant argues these exhibits were irrelevant and immaterial.
It is well established that “in a criminal case every circumstance calculated to throw any light on the supposed crime is admissible and permissible. State v. Hamilton, 264 N.C. 267, 141 S.E. 2d 506; State v. Knight, 261 N.C. 17, 134 S.E. 2d 101; State v. Ham, 224 N.C. 128, 29 S.E. 2d 449. It is not required that evidence bear directly on the question in issue, and evidence is competent and relevant if it . . . reasonably allows the jury to draw an inference as to a disputed fact.” State v. Arnold, 284 N.C. 41, 199 S.E. 2d 423 (1973). “Whether the existence of a particular state of affairs at one time is admissible as evidence of the same state of affairs at another time, depends altogether upon the nature of the subject matter, the length of time intervening, and the extent of the showing, if any, on the question of whether or not the condition has changed in the meantime.” 1 Stansbury, N. C. Evidence, § 90, p. 283 (Brandis Rev. 1973). Here, the evidence showed that *262the bottles purchased by Sheriff Jarman in 1974 looked the same as the bottles allegedly purchased by defendant in 1973; that the drugstore in question had continuously carried Singletary’s Rat Treatment since 1954; that the size bottle purchased by Sheriff Jarman in 1974 was available throughout 1973; and that the bottles bought in May, 1974 were kept in the same area of the drugstore during August ánd September of 1973. Accordingly, State’s Exhibits 2 and 3 were admissible to show that Singletary’s Rat Treatment was available at the drugstore on the day Brenda Horne testified she saw defendant purchase a bottle of liquid rat poison. Proof of this circumstance tends to bolster the State’s contention that defendant purchased a bottle of liquid rat poison at Wade’s Drugstore on 31 August 1973. Defendant’s first and fifth assignments of error are therefore overruled.
[2] Defendant next contends the trial judge improperly allowed Dr. Arthur McBay to testify as to the contents of State’s Exhibits 2 and 3 without requiring him first to relate the basis of his opinion. This contention is without merit. When an expert’s opinion is based on facts within the expert’s own knowledge he may relate those facts himself and then give his opinion; “or, within the discretion of the trial judge, he may give his opinion first and leave the facts to be brought out on cross-examination. . . .” 1 Stansbury, supra, § 136, p. 446; State v. Abernathy, 295 N.C. 147, 244 S.E. 2d 373 (1978); State v. Hightower, 187 N.C. 300, 121 S.E. 616 (1924).
Dr. McBay was qualified as an expert in toxicology and testified that he had previously tested bottles of Singletary’s Rat Treatment identical to State’s Exhibits 2 and 3. Dr. McBay then testified that Singletary’s Rat Treatment when ingested contained sufficient arsenic to kill a person. It follows that the trial judge acted within his discretion in permitting Dr. McBay to give his opinion as to the contents of State’s Exhibits 2 and 3 without requiring him to give also the basis thereof. Defendant was free on cross-examination to test fully the accuracy and validity of the tests which formed the basis of Dr. McBay’s opinion. Defendant’s eighth assignment is overruled.
Defendant contends the trial court abused its discretion by allowing the District Attorney to, ask. leading questions throughout the course of the trial. A leading question is one that *263suggests the desired answer. Frequently, questions that may be answered “yes” or “no” are regarded as leading. Even so, the trial court has discretionary authority to permit leading questions in proper instances, and absent a showing of prejudice the discretionary rulings of the court will not be disturbed. If the testimony is competent and there is no abuse of discretion, defendant’s exceptions thereto will not be sustained. State v. Young, 291 N.C. 562, 231 S.E. 2d 577 (1977); State v. Smith, 291 N.C. 505, 231 S.E. 2d 663 (1977), and cases cited therein. See generally, 1 Stansbury, supra, § 31.
We have carefully examined defendant’s exceptions and find no abuse of discretion. Eleven of the questions excepted to (Exceptions 5, 6, 7, 10, 15, 16, 22, 25, 34, 36, 37) are not leading; one (Exception 4) is not a question; two (Exceptions 30, 32) are phrased in a mode best calculated to elicit the truth; two (Exceptions 2 and 3) direct attention to the subject matter at hand without suggesting an answer; and three (Exceptions 12, 13, and 14) elicit preliminary or introductory testimony. See generally, State v. Greene, 285 N.C. 482, 206 S.E. 2d 229 (1974). In any event, we cannot say from an examination of this record that the trial judge abused his discretion or deprived defendant of a fair trial by the rulings here challenged. Defendant’s second assignment of error is overruled.
[3] Defendant next contends that, by asking certain questions, the trial judge impermissibly commented on the evidence. It is proper for a trial judge to direct questions to a witness which are designed to clarify or promote a better understanding of the testimony being given. As stated in Eekhout v. Cole, 135 N.C. 583, 47 S.E. 655 (1904): “[J]udges do not preside over the courts as moderators, but as essential and active factors or agencies in the due and orderly administration of justice. It is entirely proper, and sometimes necessary, that they ask questions of a witness so that the ‘truth, the whole truth, and nothing but the truth’ be laid before the jury.” Accord, State v. Colson, 274 N.C. 295, 163 S.E. 2d 376 (1968), cert. denied, 393 U.S. 1087 (1969). The trial judge must take care, however, that his questioning does not amount to an expression of opinion as to guilt or innocence of a criminal defendant, credibility of a witness, or any other matter which lies in the province of the jury. See State v. Hudson, 295 N.C. 427, 245 S.E. 2d 686 (1978), and cases cited therein. The trial judge commits *264prejudicial error if at any stage of the trial his questioning by its tenor, frequency, or persistence tends to convey to .the jury the impression of judicial leaning. State v. Freeman, 280 N.C. 622, 187 S.E. 2d 59 (1972); State v. Colson, supra.
Due consideration of the questions here challenged leads us to conclude that the trial judge at all times acted within the bounds of his discretion. By his questioning the trial court sought to insure that the witnesses understood what was being asked, or sought affirmation and clarification by the witness of the witness’ answer. We find nothing in any of the challenged questions which a juror could reasonably interpret as the court’s opinion on any matter before the jury. Rather, the questions posed served only to clarify and promote a proper understanding of the testimony. Defendant’s fourth, sixth, and tenth assignments of error are overruled.
[4] Defendant contends the trial court erred in allowing Dr. Page Hudson and Dr. Arthur McBay to testify to the cause of death of Joe Hunt and to the level of arsenic found in tissue analyzed by Dr. McBay. Defendant does not challenge the qualifications of the experts or the efficacy of the tests they performed. Rather, she contends the State did not sufficiently trace and identify the tissue sample that was analyzed by Dr. McBay. See e.g., State v. Britt, 291 N.C. 528, 231 S.E. 2d 644 (1977); State v. Webb, 265 N.C. 546, 144 S.E. 2d 619 (1965); Robinson v. Insurance Co., 255 N.C. 669, 122 S.E. 2d 801 (1961). This contention is without merit. The State’s evidence tends to show that Joe Hunt’s casket was exhumed on 17 April 1974 by Archie Watson, the funeral director who buried Joe Hunt, in the presence of SBI Agent Hawley. On that day Agent Hawley accompanied the casket to the Office of the Chief Medical Examiner in Chapel Hill where the casket was opened by Dr. Page Hudson who commenced an autopsy. During the course of the autopsy a piece of embalmed liver tissue was removed from the body. Dr. Hudson gave the tissue sample to Ron Boone, morgue supervisor, with instructions to deliver the tissue sample to Dr. McBay who was in the laboratory downstairs. On 17 April 1974 Dr. McBay received the embalmed liver tissue from Mr. Boone. Thus, the State’s evidence is sufficient to establish that the tissue removed by Dr. Hudson and analyzed by Dr. McBay came from the liver of Joe Hunt. Accordingly, it was permissible for Dr. McBay to testify as to the *265arsenic content of the liver as revealed by his tests and for Dr. Hudson to testify as to cause of death based, in part, on Dr. McBay’s findings. Defendant’s seventh, ninth, and eleventh assignments of error are overruled.
[5] Defendant presents several assignments relating to the judge’s charge to the jury. She first contends that in recapitulating the evidence and the contentions of the parties, the trial judge gave more stress to the evidence presented by the State. See generally, State v. Hewett, 295 N.C. 640, 247 S.E. 2d 886 (1978). This contention is unsound. Careful review of the charge indicates that the trial judge fairly and accurately summarized the evidence and contentions of both parties. The eivdence presented by the State was lengthier and more detailed than that presented by defendant. It was therefore natural and reasonable that review of the State’s evidence and contentions should take somewhat longer. See State v. Pearce, 296 N.C. 281, 250 S.E. 2d 640 (1979); State v. Sparrow, 244 N.C. 81, 92 S.E. 2d 448 (1956).
Defendant claims the trial judge committed error in stating to the jury that defendant “contended” certain things when in fact defendant did not take the stand. In context, it is clear the trial judge was properly referring to favorable evidence elicited by defendant on direct examination of her witnesses and cross-examination of State’s witnesses. See State v. Warren, 292 N.C. 235, 232 S.E. 2d 419 (1977).
Defendant alleges that the trial judge, in his recapitulation of the evidence, misstated several facts. She asserts the trial court charged that “Rozell Hunt testifed she had tried to poison Joe Hunt before, and that the Lord had saved him or that he had been saved and she did not succeed.” Defendant points out that Rozell Hunt did not testify at all and further that defense witness Sara Horne never testified to such fact.
In reviewing this contention, we first note that defendant has taken the quoted sentence out of context. The quotation is part of a sentence in which the trial judge was attempting to restate the testimony of Sara Horne. When the sentence is considered in the context in which it was used, the judge is saying that Sara Horne had testified about a conversation between Brenda Horne and her mother, ie., that her mother Rozell Hunt said she had tried to *266poison Joe Hunt before and that the Lord had saved him or that he had been saved and she did not succeed. Thus, in attempting to summarize the testimony of Sara Horne, the trial judge mistakenly attributed to Sara the earlier testimony by Brenda Horne regarding inculpatory statements made to Brenda by Rozell Hunt. In this context, the trial judge’s use of the phrase “Rozell Hunt testified," (emphasis ours) constitutes an inadvertent slip of the tongue which should have been brought to the court’s attention. Defendant, however, did not bring this inaccuracy in the recapitulation of the evidence to the attention of the trial judge so as to afford opportunity for correction; hence, it cannot now be assigned as prejudicial error. See State v. Hewett, supra; State v. Dietz, 289 N.C. 488, 223 S.E. 2d 357 (1976). Nonetheless, we note the trial judge instructed the jury that his recapitulation of the testimony did not constitute evidence and that if its recollection of the evidence differed from his, the jury’s recollection should control. Thus, assuming the slight inaccuracies in the judge’s charge were subject to appellate review, it is clear they did not constitute prejudicial error.
Defendant contends the trial judge did not properly explain the concept of reasonable doubt to the jury. This assignment is overruled. The instruction on reasonable doubt given by the trial judge is virtually identical to the instruction approved by this Court in State v. Wells, 290 N.C. 485, 226 S.E. 2d 325 (1976).
We have carefully reviewed the remaining objections to the charge and find them to be without merit. Further discussion will serve no useful purpose. In summary, the court’s charge correctly states the law and applies it to the varying aspects of the evidence in a manner calculated to assist the jury in understanding the case and in reaching a correct verdict. Assignments of error 12, 13, 14, 15, 16 and 18 are therefore overruled.
Another assignment relating to the charge — No. 17 — is not presented and discussed in defendant’s brief. It is therefore deemed abandoned under Rule 28, Rules of Appellate Procedure.
No prejudicial error having been shown in defendant’s trial, the judgment of the trial court must be upheld.
No error.