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Current Medical Literature: A Quantitative Survey of Articles and Journals

ESTELLE BRODMAN and SEYMOUR I.TAINE

The traditional view of scientific, especially medical, literature is that its volume is so large that it has become impossible to bring it under control by traditional methods. So far as can be ascertained from a reading of the reports on this problem, most previous estimates of the size of the literature have been made either entirely on an a priori basis or by extrapolation from incomplete data. In the latter category, especially, belong estimates based on partial counts of the number of journals published.

Years of experience spent in examining thousands of medical serials convinced us that the use of the journal title as the quantitative unit of the periodical literature was both erroneous and misleading. Since it is the individual article that contains the specific medical information sought, it seemed logical to use this unit as the basis for determining the true size and therefore the indexing load. The results of some trial projects confirmed this subjective impression and also indicated the feasibility of a larger investigation based on the count of periodical articles within the separate journal issues. The present study was undertaken to procure these data; its further aim was to analyze the information obtained, to compare the results with some other studies made on the traditional journal title basis, and, finally, to draw some conclusion regarding the significance of the findings.

The National Library of Medicine makes a planned, regular, and continuing attempt to learn of the existence of and to obtain all the medical serials published throughout the world. As a result of this policy the Library at the end of 1957 held more than 13,000 different substantive and non-substantive serial titles of reasonable currency. For purposes of this study, it was assumed that

ESTELLE BRODMAN and SEYMOUR I.TAINE National Library of Medicine, Washington, D.C.



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--> Current Medical Literature: A Quantitative Survey of Articles and Journals ESTELLE BRODMAN and SEYMOUR I.TAINE The traditional view of scientific, especially medical, literature is that its volume is so large that it has become impossible to bring it under control by traditional methods. So far as can be ascertained from a reading of the reports on this problem, most previous estimates of the size of the literature have been made either entirely on an a priori basis or by extrapolation from incomplete data. In the latter category, especially, belong estimates based on partial counts of the number of journals published. Years of experience spent in examining thousands of medical serials convinced us that the use of the journal title as the quantitative unit of the periodical literature was both erroneous and misleading. Since it is the individual article that contains the specific medical information sought, it seemed logical to use this unit as the basis for determining the true size and therefore the indexing load. The results of some trial projects confirmed this subjective impression and also indicated the feasibility of a larger investigation based on the count of periodical articles within the separate journal issues. The present study was undertaken to procure these data; its further aim was to analyze the information obtained, to compare the results with some other studies made on the traditional journal title basis, and, finally, to draw some conclusion regarding the significance of the findings. The National Library of Medicine makes a planned, regular, and continuing attempt to learn of the existence of and to obtain all the medical serials published throughout the world. As a result of this policy the Library at the end of 1957 held more than 13,000 different substantive and non-substantive serial titles of reasonable currency. For purposes of this study, it was assumed that ESTELLE BRODMAN and SEYMOUR I.TAINE National Library of Medicine, Washington, D.C.

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--> the number of medical serials, particularly those of a substantive nature, not received at the National Library of Medicine was so small and was probably scattered so widely in terms of subject, language, and country of origin, it would not distort the results obtained. The field of medicine is broadly defined by the Library; it includes the ancillary fields of dentistry, nursing, hospital administration, pharmacy, homeopathy, and osteopathy. Methods A modest, part time investigation was set up in the National Library of Medicine. Because of limitations of time, staff, and equipment, only certain data were tabulated and these were analyzed for the most part by hand methods. All current serials coming to the National Library of Medicine for a three-month period (March-May, 1957) were initially divided into two categories: those indexed by the Current List of Medical Literature and those not so indexed. Since the information about the journals in the Current List was already available for previous operational purposes, nothing further was done with this group of titles. Material not indexed by the Current List was next sorted into two further groups: those containing substantive articles (“indexable journals”) and those containing merely news items, abstracts, statistics, and other non-substantive miscellany (“non-indexable journals”). The number of individual journal issues in each group was counted, after which the non-indexable journals were discarded from this study; the remaining journals, the indexable journals, were analyzed for the following information: Number of articles contained in the journal. Periodicity of the journal and its articles. Language or languages of the journal and its articles. Country of origin of the journal and its articles. Subject or subjects covered by the journal and its articles. (Subject categories used were adapted from the first edition of World Medical Periodicals.) The information thus obtained was added to equivalent information for the journals and articles indexed in the Current List of Medical Literature to obtain the total picture. The findings were then compared with those of two earlier, somewhat similar studies, that of the Welch Medical Library Indexing Project (1) and that of the second edition of World Medical Periodicals (2) wherever possible.

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--> Findings A total of 31,423 articles appearing in 2089 journal titles was counted in the three-month period for an annual total of 125,692 articles not indexed in the Current List of Medical Literature. By utilizing the periodicity data and by making an adjustment for the journals issued annually, semiannually, or at irregular intervals which would normally not be received in any single quarter, the annual number of journal titles and issues was estimated to be 2506 and 19,007 respectively. However, because all the current journals, irrespective of their subject fields, which were received in the National Library of Medicine during the three-month period were counted, many items are included which would not be indexed in a general medical index, which, by its subject scope, would be more restrictive than the collecting policy of the Library. For example, while material on bibliography, physics, and chemistry is admitted to the Library collection, it would be excluded from a medical index. If we remove from the count the out-of-scope items, the grand totals of indexable medical materials are reduced by 135 journals, 1165 issues, and 14,436 articles to the figures which appear in Table 1. Throughout the paper, we have used the maximum counts to be certain that we have not erred on the side of under-estimation. Furthermore, no deductions have been made for the considerable quantity of articles in journals in such non-clinical fields as general science, general biology, and psychology which would also not be indexed in a general medical index. TABLE 1 National Library of Medicine Survey, 1957: Summary table Substantive serial titles (per year) Number indexed in Current List of Medical Literature 1,508   Number of additional titles found 2,371   Total substantive serial titles   3,879 Substantive serial issues (per year) Number indexed in Current List of Medical Literature 11,434   Number of additional issues found 17,843   Total substantive serial issues   29,277 Substantive serial articles (per year) Number indexed in Current List of Medical Literature 107,478   Number of additional articles found 111,256   Total substantive serial articles   218,734 From these figures it appears that the total indexable medical periodical lit-

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--> erature is just about double the size of the present Current List of Medical Literature, the largest medical index in the world. PERIODICITY The frequency with which the material is published is given in Table 2. TABLE 2 Periodicity of medical literature   Periodical Titles Periodical Issues Periodical Articles Periodical Articles per Title Frequency Number % Number % Weekly 64 1.6 3,588 18,354 8.3 270 Semimonthly 75 1.9 2,040 12,336 5.9 145 Monthly 1220 30.4 15,240 99,107 44.8 79 Bimonthly 639 15.9 3,994 33,122 14.9 51 Quarterly 953 23.7 3,892 29,975 13.5 31 Semiannually 126 3.1 252 2,149 1.0 17 Annually 369 9.2 369 6,303 2.8 17 Irregularly 568 14.1 1,136 20,280 9.1 36 Total 4014 99.9 30,441 221,626 100.3 — It can be seen that in regard to productivity the rank order follows closely the frequency of appearance of the journal. The most frequently appearing type of journal (the weekly) contains more articles per year than the semimonthly, which in turn, contains more articles per year than the monthly, and so on down to the annual publication. This information, often guessed at and now confirmed, is of some interest. For example, the data indicate that whereas the total number of annual, semiannual, and irregularly appearing journals comprise more than a quarter of all journals by title, the indexing workload in terms of articles is actually under 13%. Stated another way, a decidedly misleading impression could be created by the isolated fact that a particular 1063 journals are indexed, since these yield a total of only 28,732 articles. It is also interesting to note that while overall there is an average of 58.1 articles published per year in each medical journal, the titles now indexed in the Current List yield 71.3 articles per year per title. Also, the average number of articles per journal issue for Current List titles is 9.4 while the same figure for non-Current List journals is only 7.6 articles per issue. This would seem to indicate that Current List journals are more productive than non-Current List titles in numbers of articles they contain; if so, it would mean that indexing of the additional journals would not swell the total in direct proportions to the number added. GEOGRAPHIC ORIGINS During the three-month period, journals from 85 countries were received. The results are tabulated in Table 3. However, some of the smaller nations

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--> known to publish at least one medical periodical did not contribute any specimens during the collection period. Quantitatively, both by titles and articles, these omissions should not be significant. TABLE 3 Geographic distribution of medical literature   Periodical Titles Periodical Articles In Current List All periodical titles In Current List All periodical articles Country Number % Number % Algeria 3 6 ★ 291 327 ★ Argentina 25 55 1.52 1,892 3,784 1.7 Australia 6 15 ★ 576 896 ★ Austria 20 45 1.24 1,130 2,222 1.0 Albania 0 1 ★ 0 56 ★ Belgium 36 52 1.44 1,791 2,691 1.2 Brazil 33 90 2.49 1,127 3,335 1.5 British West Indies 2 2 ★ 39 39 ★ Bulgaria 5 5 ★ 387 387 ★ Burma 1 1 ★ 29 29 ★ Canada 20 55 1.38 1,494 2,662 1.2 Ceylon 1 2 ★ 15 37 ★ China 6 14 ★ 422 998 ★ Chile 6 14 ★ 270 642 ★ Colombia 2 15 ★ 40 360 ★ Costa Rica 1 2 ★ 15 47 ★ Cuba 11 32 ★ 298 918 ★ Canary Islands 0 1 ★ 0 24 ★ Cyprus 1 1 ★ 10 10 ★ Czechoslovakia 24 30 ★ 1,613 1,785 ★ Denmark 19 41 1.14 1,076 1,824 ★ Dominican Republic 1 2 ★ 12 92 ★ Ecuador 1 7 ★ 16 176 ★ Egypt 2 7 ★ 134 262 ★ England 97 244 6.76 8,058 16,398 7.4 Finland 7 16 ★ 313 593 ★ France 116 297 8.23 10,997 22,485 10.2 French Guiana 1 1 ★ 40 40 ★ Formosa 0 1 ★ 0 48 ★ Germany 136 315 8.72 12,449 25,741 11.7 Greece 2 11 ★ 65 449 ★ Guatemala 1 3 ★ 40 96 ★ Hawaii 1 1 ★ 36 36 ★ Haiti 0 2 ★ 0 32 ★ Honduras 1 1 ★ 20 20 ★ Hungary 18 23 ★ 1,288 1,388 ★ India 8 42 1.16 493 2,761 1.3 Indonesia 1 2 ★ 60 68 ★ Italy 150 345 9.55 8,668 17,192 7.8 Iran 1 3 ★ 45 181 ★ Israel 3 9 ★ 200 344 ★ Ireland (Eire) 2 4 ★ 144 160 ★ Iraq 1 2 ★ 20 36 ★ Japan 22 187 5.18 1,081 19,665 8.9 Jordan 0 1 ★ 0 8 ★ Kenya 1 1 ★ 66 66 ★

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-->   Periodical Titles Periodical Articles In Current List All periodical titles In Current List All periodical articles Country Number % Number % Lebanon 2 5 ★ 118 162 ★ Luxembourg 1 1 ★ 5 5 ★ Malaya 2 3 ★ 44 92 ★ Martinique 1 1 ★ 6 6 ★ Mexico 13 42 1.16 488 1,296 ★ Morocco 1 2 ★ 180 180 ★ Madagascar 0 1 ★ 0 72 ★ Netherlands 28 63 1.75 1,733 3,017 1.4 New Zealand 2 9 ★ 74 230 ★ Nicaragua 0 1 ★ 0 56 ★ Northern Ireland 1 1 ★ 20 20 ★ Norway 2 17 ★ 212 632 ★ New Guinea 0 1 ★ 0 12 ★ Pakistan 1 6 ★ 20 200 ★ Panama 1 3 ★ 30 142 ★ Paraguay 0 1 ★ 0 8 ★ Peru 2 16 ★ 20 288 ★ Philippines 3 13 ★ 130 450 ★ Poland 34 44 1.22 1,756 2,396 1.1 Portugal 10 31 ★ 499 1,007 ★ Puerto Rico 1 4 ★ 60 104 ★ Rhodesia and Nyasaland Federation 1 1 ★ 48 48 ★ Rumania 9 22 ★ 309 1,737 ★ Saarland 1 1 ★ 12 12 ★ Salvador 1 1 ★ 37 37 ★ Scotland 4 6 ★ 134 150 ★ South Africa 3 19 ★ 248 876 ★ Spain 33 117 3.24 1,491 5,231 2.4 Sweden 17 42 1.16 1,755 2,567 1.2 Switzerland 59 112 3.10 2,863 5,203 2.4 Thailand 0 3 ★ 0 120 ★ Trieste 1 1 ★ 31 31 ★ Tunisia 1 1 ★ 90 90 ★ Turkey 3 12 ★ 132 488 ★ U.S.A. 391 847 23.46 31,751 53,975 24.5 U.S.S.R. 57 84 2.33 5,338 7,126 3.2 Uruguay 6 14 ★ 109 309 ★ Venezuela 4 16 ★ 116 412 ★ Yugoslavia 17 28 ★ 859 1,439 ★ Total 1508 3597 — 107,478 221,626 — ★Under 1%. By far the largest producer of medical periodical literature, on any basis, is the United States, which furnishes almost one-quarter of all the world’s journals and/or articles. Although in number of journals Italy ranks second to the U.S. with 9.6%, with Germany (8.7%), France (8.2%), and England (6.8%) trailing in that order, on the basis of articles, Germany ranks second with

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--> 11.7%, followed in order by France (10.2%), Japan (8.9%), and Italy (7.8%). This qualitative and quantitative variation of the “Big 5” is made especially interesting by the leap into fourth place by Japan which now produces almost 20,000 articles yearly. Oddly, a national pattern appears to emerge in regard to the average number of articles published in each journal title. As Table 4 indicates, the journals of certain countries are consistently characterized by a high number of articles, others are of a low productivity, and a third group can be described as medium producers: TABLE 4 Average number of articles per title by country High Medium Low Japan 105.2 India 65.7 Italy 49.8 U.S.S.R. 84.8 U.S.A. 62.6 Switzerland 46.5 Germany 81.7 Sweden 61.1 Spain 44.7 LANGUAGES As shown in Table 5, twenty languages are utilized to convey practically all of the world’s medical information in periodicals. The heading “Polylingual” TABLE 5 Language breakdown of medical literature   Periodical Titles Periodical Articles In Current List All periodical titles In Current List All periodical articles Language Number % Order Number % Order Chinese 4 12 .3 20 362 938 .4 15 Czechoslovakian 20 25 .7 14 1,470 1,690 .8 12 Danish 5 26 .7 13 368 924 .4 15 Dutch 10 33 .9 11 996 2,000 .9 11 English 607 1,375 38.2 1 45,651 82,687 37.3 1 Finnish 3 10 .3 21 134 402 .2 17 French 152 384 10.7 3 13,358 28,254 10.9 3 German 155 394 10.9 2 13,681 28,729 13.0 2 Hungarian 14 16 .4 18 1,037 1,137 .5 14 Italian 151 352 9.8 5 8,699 16,699 7.5 5 Japanese 1 128 3.5 7 108 17,232 7.8 4 Norwegian 1 13 .4 19 144 536 .2 17 Polish 31 39 1.1 10 1,702 2,302 1.0 10 Polylingual 110 132 3.7 6 5,900 7,316 3.3 7 Portuguese 42 121 3.4 8 1,584 4,356 1.5 9 Rumanian 7 19 .5 17 224 1,804 .8 12 Russian 56 75 2.1 9 5,290 6,930 3.1 8 Serbo-Croatian 14 24 .7 15 697 1,173 .5 14 Spanish 109 358 9.9 4 5,190 13,806 6.2 6 Swedish 2 22 .6 16 46 770 .3 16 Turkish 3 10 .3 22 132 456 .2 17 Other 11 28 .8 12 705 1,485 .7 13 Total 1508 3597 99.9   107,478 221,626 99.5  

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--> refers to the journals which include articles written in more than a single language; “Other” includes all material in a single language other than the twenty already listed for which fewer than 10 journal titles were located. Table 5 shows that English is by far the most common language (over 37% of the articles). Here again, as in the geographic breakdown, a similarly intriguing variation between journal and article counts emerges. In regard to journals, German ranks second with 10.9%, followed very closely by French (10.7%); Spanish and Italian run a close fourth and fifth, with 9.9% and 9.8% respectively. On the article basis, German is again second to English with 13%, just slightly ahead of French at 12.9%. Fourth place is, however, usurped by Japanese with 7.8%, and Italian is in fifth with 7.5%. Russian trails far behind in eighth place with a little over 3% of the total. Some quick arithmetic reveals the interesting fact that about 85% of the medical periodical literature is written in but six languages. SUBJECTS Any attempt to subdivide the field of medicine into its component parts is, at best, a frustrating procedure and rarely, if ever, does it produce a result that is completely satisfying. Much of the difficulty, apart from the ever-broadening scope of medicine, may be attributed to the inherent characteristics of the various related subject fields and specialties which resist a clean, sharp, and exclusive compartmentalization. For example, the subject field under which the greatest quantity of medical periodical literature falls is known as “general medicine.” Actually, the specific articles which appear within these general medical journals can be distributed without strain among the different smaller subdivisions provided in the classification. Unfortunately, because of time limitations, the present study had to change its basis and restrict the subject breakdown of the collected material to the journal title and not, as in other cases, to the individual article itself. Despite these solid reservations, the figures in Table 6 are still of interest and value, although more limited than might be hoped. Its greatest usefulness will probably be found in the data for the more easily circumscribed fields such as dermatology and ophthalmology. Comparison with other studies The findings of this investigation can be profitably compared with those of the Welch Medical Library Indexing Project and the second edition of the World Medical Periodicals. Unfortunately the latter work appeared just at the conclusion of the National Library of Medicine survey; it is to be regretted that

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--> TABLE 6 Subject breakdown of medical literature   Periodical Titles Periodical Articles In Current List All periodical titles In Current List All periodical articles Subject Number % Number % Alcoholism 2 12 ★ 55 227 ★ Allergy 6 7 ★ 273 493 ★ Anatomy (incl. embryology) 33 48 1.2 1,231 2,303 1.0 Anesthesiology 12 17 ★ 647 1,363 ★ Anthropology 2 14 ★ 66 470 ★ Antibiotics 8 11 ★ 635 687 ★ Aviation Medicine 8 8 ★ 223 223 ★ Athletics 0 10 ★ 0 524 ★ Bibliography 1 20 ★ 52 596 ★ Biochemistry 31 37 1.1 3,099 3,491 1.5 Biology, general 21 54 1.4 1,194 2,778 1.1 Beauty culture 0 2 ★ 0 56 ★ Cancer 26 34 1.0 1,603 1,815 ★ Cardiovascular system 29 43 1.1 1,426 2,614 1.1 Chemistry 1 37 1.0 12 9,260 4.1 Chiropody 1 9 ★ 60 268 ★ Chiropractic 0 5 ★ 0 248 ★ Chronic disease 1 1 ★ 108 108 ★ Criminology 0 9 ★ 0 260 ★ Civil Defense 0 1 ★ 0 64 ★ Dentistry 4 180 4.5 456 8,296 3.4 Dermatology 29 50 1.3 2,117 3,625 1.5 Diabetes 1 7 ★ 51 187 ★ Education 0 2 ★ 0 92 ★ Endocrinology 17 21 ★ 1,192 1,396 ★ Engineering 0 1 ★ 0 72 ★ Enzymology 5 5 ★ 114 114 ★ Experimental medicine 88 101 2.5 5,755 6,383 2.6 Food technology 1 10 ★ 49 669 ★ Gastroenterology 18 29 ★ 1,167 2,779 1.1 General medicine 332 817 20.4 33,143 60,147 24.5 Genito-urinary system 19 27 ★ 1,103 1,743 ★ Geriatrics 5 11 ★ 289 517 ★ Gynecology and obstetrics 48 76 1.9 3,393 5,369 2.2 Hematology 17 24 ★ 786 1,322 ★ Heredity and genetics 13 22 ★ 321 649 ★ History of medicine 8 24 ★ 126 566 ★ Homeopathy 2 22   208 972 ★ Hospitals 8 47 1.2 957 2,949 1.2 Hydrology and climatology 1 14 ★ 24 764 ★ Hygiene and public health 42 162 4.1 2,207 5,799 2.4 Hypnosis 0 2 ★ 0 44 ★ Illustration, etc. 4 5 ★ 115 143 ★ Immunology 11 11 ★ 421 421 ★ Industrial hygiene 20 45 1.1 988 2,224 1.0 Infectious diseases 24 31 ★ 1,426 1,826 ★

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-->   Periodical Titles Periodical Articles In Current List All periodical titles In Current List All periodical articles Subject Number % Number % Internal medicine 14 21 ★ 1,091 1,631 ★ Jurisprudence, medical 8 21 ★ 253 753 ★ Leprosy 4 8 ★ 83 195 ★ Malaria 3 5 ★ 80 140 ★ Maternity and child welfare 0 14 ★ 0 532 ★ Medical profession 3 13 ★ 177 953 ★ Medical technology 10 19 ★ 435 755 ★ Medicine and religion 0 8   0 360 ★ Microbiology 42 54 1.4 2,728 3,360 1.4 Microscopy 4 7 ★ 133 313 ★ Military and naval medicine 37 44 1.1 1,491 1,679 ★ Mycology 1 2 ★ 2 150 ★ Naturopathy 0 6 ★ 0 468 ★ Neurology 50 71 1.8 2,625 3,433 1.4 Neurosurgery 11 13 ★ 454 642 ★ Nursing 5 45 1.1 531 2,483 1.0 Nutrition 16 32 ★ 1,018 1,630 ★ Occupational therapy 7 25 ★ 348 920 ★ Ophthalmology 40 76 1.9 2,306 4,302 1.8 Orthopedics 18 44 1.1 1,022 2,194 ★ Osteopathy 1 18 ★ 144 784 ★ Otorhinolaryngology 35 60 1.5 2,146 3,250 1.3 Parasitology 16 23 ★ 748 1,288 ★ Pathology 36 46 1.2 2,537 3,257 1.3 Pediatrics 59 92 2.3 3,778 5,694 2.3 Pharmacology 34 39 1.0 2,462 2,782 1.1 Pharmacy 15 113 2.8 767 4,487 1.8 Philosophy 0 2 ★ 0 76 ★ Physics 12 26 ★ 1,328 2,956 1.2 Physiology 44 48 1.2 3,337 3,561 1.5 Physiotherapy 13 33 ★ 556 1,508 ★ Plastic surgery 3 6 ★ 190 382 ★ Population 0 3 ★ 0 180 ★ Psychiatry 63 103 2.6 3,086 3,974 1.6 Psychoanalysis 8 15 ★ 292 468 ★ Psychology 27 73 1.8 1,325 3,581 1.5 Plants 0 7 ★ 0 476 ★ Radiodiagnosis, etc. 29 48 1.2 2,452 3,300 1.3 Red Cross 0 6 ★ 0 208 ★ Rheumatism 13 20 ★ 535 659 ★ Science, general 10 76 1.9 1,865 8,713 3.6 Serology 4 4 ★ 169 169 ★ Sex 0 3 ★ 0 112 ★ Social medicine 6 16 ★ 280 688 ★ Sociology 0 13 ★ 0 920 ★ Speech disorders 2 5 ★ 74 162 ★ Statistics 0 2 ★ 0 264 ★ Surgery 106 193 4.8 8,227 12,903 5.3

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-->   Periodical Titles Periodical Articles In Current List All periodical titles In Current List All periodical articles Subject Number % Number % Therapeutics 10 49 1.2 624 2,768 1.1 Thorax 15 30 ★ 795 1,659 ★ Tropical medicine 33 39 1.0 1,474 1,590 ★ Tuberculosis 32 62 1.6 1,617 2,549 1.0 Veterinary medicine 5 47 1.2 532 3,732 1.5 Vitaminology 5 7 ★ 156 400 ★ Zoology 1 14 ★ 90 1,146 ★ Total 1809 3994 — 123,455 244,455 — ★Less than 1%. time and staff were not available to do a thorough comparison of the two lists, especially in the language, country, and periodicity areas. It is to be hoped that further work can be done on this in the future. The Welch Library Indexing Project, sponsored by the predecessors of the present National Library of Medicine, carried on its work from 1948 to 1953. Among its other activities, the Project also undertook to do a comprehensive survey of the world’s medical serials. Table 7 gives comparative figures of the total number of journals studied by the three groups. TABLE 7 Comparative counts of medical periodicals Welch Medical Library Indexing Project Survey 4454 World Medical Periodicals 4360a National Library of Medicine Survey 3879 a Current titles only. The differences between the National Library of Medicine figure and those of the other two are not as significant as would appear at first glance. The Welch Medical Library figures are higher on account of differences in definition of current substantive periodicals. Actually, an adjustment on the basis of like criteria would probably effect an extremely close alignment; this is not surprising in view of the wide use made by the Indexing Project of the serial holdings of the National Library of Medicine. The apparent discrepancy between the National Library of Medicine and World Medical Periodicals is almost entirely due to the coverage from two specific geographic areas in the National Library of Medicine. The National Library of Medicine is now overcoming a lag in the acquisition of materials from Latin-America and Japan occasioned by an earlier policy decision to collect selectively from these regions. Some 90% of the differential between the two

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--> totals appears to consist of Latin-American journals whose average output of articles is generally acknowledged to be quite low. Tables 8 to 10 are comparisons of the results in terms of journal titles of the National Library of Medicine and of the Welch Medical Library Indexing Project. In spite of the time interval between the two investigations, there is a high degree of correlation; 0.905 for periodicity and 0.947 for languages, for example. TABLE 8 Comparison of periodicity of medical journals   National Library of Medicine Survey Welch Medical Library Indexing Project Survey Frequency Number % Number % Weekly 64 1.6 93 2.0 Semimonthly 75 1.9 95 2.0 Monthly 1220 30.4 1518 34.0 Bimonthly 639 15.9 603 14.0 Quarterly 953 23.7 868 19.0 Semiannually 126 3.1 73 1.6 Annually 369 9.2 385 9.0 Irregularly 568 14.1 822 18.4 Total 4014 99.9 4454 100.0 TABLE 9 Comparison of geographic origin of medical journals   National Library of Medicine Survey Welch Medical Library Indexing Project Survey Geographic Division Number % Number % Europe 2015 55.9 2012 47.2 North America 944 26.2 1382 31.0 Asia 295 8.2 336 7.5 Latin America 283 7.9 523 11.7 Africa 38 1.1 45 1.0 Australasia 25 .7 39 .9 Other 0 0 27 .6 Total 3597 100.0 4454 99.9 TABLE 10 Comparison of languages of medical journals   National Library of Medicine Survey Welch Medical Library Indexing Project Survey Language Number % Number % English 1375 38.2 2061 41.2 German 394 10.9 545 10.9 French 385 10.7 600 12.0 Spanish 358 9.9 608 12.1 Italian 352 9.8 348 6.9 Polylingual 132 3.7 0 0 Japanese 128 3.5 187 3.7 Portuguese 121 3.4 196 3.9 Russian 75 2.1 85 1.7 Polish 39 1.1 34 .7 Dutch 33 .9 49 1.0 Danish 26 .7 39 .8 Czechoslovakian 25 .7 38 .8 Serbo-Croatian 24 .7 22 .4 Swedish 22 .6 46 .9 Rumanian 19 .5 1 0

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--> TABLE 10 Comparison of languages of medical journals   National Library of Medicine Survey Welch Medical Library Indexing Project Survey Language Number % Number % Hungarian 16 .4 26 .5 Norwegian 13 .4 14 .3 Chinese 12 .3 1 0 Finnish 10 .3 17 .3 Turkish 10 .3 21 .4 Less than 10 28 .8 70 1.4 Total 3597 100.0 5008 99.9 Summary An investigation was undertaken to determine the approximate size and composition of present-day medical periodical literature by employing as the basic counting unit not the journal title, so frequently used in such investigations, but the journal article. Our object was to do away with the difficulty encountered in most previous studies, where certain assumptions had to be made about the relationship between journal titles and journal articles. Data were collected on the number of journal titles and journal articles published in 1957, their periodicity and country of origin, the languages in which they were published, and their subject breakdown. Analysis of these data showed a direct linear relationship between the number of issues of a journal published (its periodicity) and the number of articles in it. On the other hand, there appears to be a true variation in the average number of articles published per journal title on the basis of the geographical origin of the journal, and linguistically, substantial deviations are encountered between journal title counts and article counts. It was also possible to analyze the data of the medical periodical literature for the probable magnitude of what would logically be indexed in a general medical index. This turns out to be about 220,000 articles per year, or approximately twice the number already listed in the Current List of Medical Literature, the largest general medical index we now possess. We believe the statistics presented here can be used meaningfully in additional ways, only a few of which are mentioned in this paper. It is to be hoped that further work can be undertaken in the future. REFERENCES 1. WILLIAMINA A.HIMWICH and others. Survey of world medical serials and coverage by indexing and abstracting service, Welch Medical Library indexing project sponsored by the Armed Forces Medical Library. Baltimore, 1954. 2. LESLIE T.MORTON, comp. World medical periodicals, 2nd edition, World Medical Assoc., Geneva, 1957.

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