Clinical Anatomy 957-59 (1996)
Learning Gross Anatomy: Dissection and Prosection VERNON L. YEAGER
Department of Anatomy and Neurobiology, S t . Louis IJniversity S'dooL of Medirine, S t . Louis, Mi.wuri
The gross anatomy course at St. Louis University School of Medicine consists of 40 regions or units covering the entire body and utilizes peer teaching in which students do every fourth dissection. One-fourth of the students learn each unit by dissecting; three-fourths learn from predissected material. Four multiple choice tests were studied to determine whether students scored better on questions on units they dissected than those who learned from predissected material. Results were adjusted on the basis of students' scores on whole tests. There were four teams of students and four tests resulting in 16 sets of questions. Dissectors scored better than nondissectors in 13 sets, but the overall differences were small (67.80 vs. 66.70). It is con- cluded that there is a small advantage gained from dissecting and demonstrating to their peers, but that learning from dissected cadavers is a satisfactory method of study, since our students traditionally score above the national average on the anatomy portion of the National Board Examination. o 1996 Wiley-Li\s, Inc
Key words: gross anatomy, teaching, prosection
In a recent issue of this journal, three articles debated whether or not every medical student should dissect the whole body or learn from predissected bod- ies (Newell, 1995; Shaw-Dunn, 1995; Skidmore, 199.5). This argument has gone on for years and there is rhetoric both pro (Beahrs, 1991; Mottershead, 1980; Newell, 1995; von Ludinghausen, 1992; Willson et al., 1975) and con (Callahan and Gavan, 1968; Ferm and Lyons, 1971; King et al., 1994; Nnodim, 1990; Sinclair, 1965; Skidmore, 199.5; Yeager and Young, 1992). But the rhetoric is just rhetoric with very little research to back it up. T h e attempts at research, for the most part, compared classes of lengths or different students (Sin- clair, 196.5; Wilson et al., 1975) and the results appear to be more judgmental than experimental.
St. Louis IJniversity School of Medicine designed a course in 1972 (Yeager and Young, 1992) that reduces course time but retains dissection in an effective way and lends itself to a study comparing grades of dissec- tors and nondissectors. This is a single course with all students attending the same lectures, review sessions, laboratories, and examinations. T h e number of assigned course hours is 164 exclusive of time for examinations. I t consists of 40 assigned regions or units that cover the entire body. Eight students assigned alphabetically to
each body are divided into four teams. Each team does every fourth dissection, then demonstrates that unit to the other three teams. Therefore, students study some units by dissecting and other units from predissected material. While the dissectors are dissecting, the nondissectors are free to study for other courses. All students are allowed to study the dissected material at any time.
This study was made during the school year 1993-1994. Four sets of examinations consisting of practical, multiple choice written and slide tests were given, but for this report, only the results of the written tests were used. T h e first three tests covered only new material, but the final examination was comprehensive. For each test, all students were dissectors of some units and nondissectors for other units, thus serving as their own controls. For this study, students repeating the course or who switched teams during the course were eliminated, leaving 39 or 40 students in each team. T h e
Received for publication August 4, 1994; revised M a y 9, 1995.
Address reprint requests to Vernon L. Yeagcr, Department of Anatomy and Neurobiology, St. Louis IJniversity School of hledi- cine, 1402 South Grand Boulevard, St. I,ouis, MO 63104.
0 1996 Wiley-Liss, Inc.
grades of dissectors on questions dealing with units they dissected were compared to grades of nondissec- tors on the same questions. T h e test-taking ability of the teams was not equal, so grades were adjusted to eliminate those differences.
Because there were four teams and four examina- tions, 16 sets of results were compared. In two cases, t he nondissectors scored higher than dissectors, in one case they scored equally, and in 13 cases the dissectors scored higher than the nondissectors. T h e average grade, based on percentage of correct answers, for dis- sectors was 67.80 compared to 66.70 for nondissectors, a difference of 1.10. In no case was the difference sta- tistically significant. (Of course, students who missed getting an A, B, C, or a passing grade by 1.10 points may have felt the difference was signficant.) T h e nondissectors had higher or equal grades to dissectors only in the first half of the course, and the greatest dif- ference occurred on the final comprehensive test where the difference was 2.10.
T h e results show that students learn gross anatomy nearly as well from predissccted cadavers as by dis- secting and teaching. T h e fact that the greatest differ- ence was on the comprehensive final test may indicate that it takes time for students to learn how to get the most out of dissecting and that doing the dissections may aid in retaining their knowledge.
In 1955, the average time devoted to gross anatomy at 87 schools in the lJnited States and Canada was 330 hours (Hoerr, 1956). Nearly 40 years later, 123 schools averaged 182 hours (Collins et al., 1994). I t was also shown that in 99 of 102 schools, dissection was a part of the gross anatomy course, but three schools required no dissection. T h e course at St. Louis [Jniversity reduces course time but retains dissection in an effective way (Yeager and Young, 1992). It was shown that the course could be taught utilizing half the cadavers of a traditional course, have less contact hours than the national averagc, yet students did better than average on the anatomy part of the National Board Examination.
T h e St. Louis gross anatomy course has two different activities, dissecting and demonstrating (teaching), that help make the study of predissected bodies more mean- ingful. ' rhe dissector sees the whole anatomy, not just the named structures seen after the dissection is com- plete or shown in atlases. Because every student does some dissecting in every region of the body, the insight to the total anatomy is carried over to the units they do not dissect. It is believed that this is why there was so little difference between grades on questions from units dissected and questions from units not dissected. T h e demonstration or teaching of the anatomy to the nondis-
sectors is a separate activity. T h e slight difference (1.10) between the grades of dissectors compared to nondis- sectors might be the result of teaching, not dissecting, but this was not determined in this study.
T w o things are important: (1) all students should have access to study the dissected bodies at all times, and (2) students should do some dissecting in all major regions of the body.
For 12 years between 1972 and 1985, the gross anatomy unit examination of the National Board of Medical Examiners was given as the final examination for our course, and the average score for our students on those examinations was 604. Our students have al- ways scored above the national average on the anatomy part of the National Board Part I examination since this course was instituted.
Ferm and Lyons (1971) suggest that most of the time spent in the gross anatomy course should be utilized for the development of a working vocabulary. 'The present author strongly rejects that suggestion. Most of the time spent in the gross anatomy course should be in devel- oping a three-dimensional mental picture of the anatomy of a living patient. Learning vocabulary is a part of that. T h e most important learning aid is the cadaver, not the lecture, atlas, or textbook.
T h e author thanks Dr. John Haring for doing statis- tics for this study, and Dr. Paul A. Young for reading the manuscript.
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