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The number of users on the MEDLARS system varied more during nonprime time than on prime time; there were times of higher than average use and times of much lower use. This variation in the number of users influenced search time. The study found a variation of as much as 19% from the mean search time for times of high use versus times of low use. Added-time formulas showed the additional time allowed for a search on nonprime time before costs would equal those for the same search on prime time. (For example, a search with four citations that took five minutes on prime time could take up to eight minutes and thirty seconds on nonprime time before costs would be equal.) In all examples, nonprime time searching was the most cost-effective alternative.

Hierarchically structured thesauri--including MeSH--were studied to test the assumption of an inverse relationship between term specificity and the number of postings in online databases. It was suggested that this assumption holds only for peripheral terms and that the opposite is true for the central terms of a discipline. The Environment tree structure of MeSH was used to test the "peripheral" hypothesis, which was supported at a .05 level of significance, but the scattergram on the Endocrine Diseases tree, which was run to test the "central" hypothesis, had an even better level, .02. The commonly held belief that specific terms are added to a thesaurus when more general ones get too many postings was also tested. The relationship between specificity and dates was supported in MeSH (.015). The corollary--that terms with later dates have fewer postings--was supported at a .001 level of significance. The results for MeSH were much more significant than for other hierarchically structured thesauri, which indicates that thesaurus development at NLM involves interaction with MEDLINE to preclude an excessive number of postings to any one term.

As libraries evolve into database management centers with network capabilities, they increasingly serve users who are remotely situated from them. This paper explores some of the problems encountered by a national association library in serving the remote user. User satisfaction is evaluated, procedures are subsequently modified, and satisfaction is again measured to determine variables that affect user response to the services.

The rise of dentistry from a mechanical trade to a profession has often been attributed to the so-called "triumvirate" of organization, education, and journal literature. This essay focuses on one part of the triumvirate, examining the role of journals in the growth of dentistry as a profession, from the appearance of the first journal in 1839 to the publication of the Index to Dental Literature in 1921. Rather than discussing the history of individual titles, it identifies some of the broader issues and problems that confronted early dental journalism. The evolution of dental journals from trade house publications to independent scientific literature mirrored the movement toward professional status in dentistry during the late 19th and early 20th centuries.

Numerous medical libraries house archival collections. This article discusses criteria for selecting personal papers of biomedical scientists and physicians for a medical archives and defines key terms, such as appraisal, manuscripts, papers, records, and series. Appraisal focuses on both collection and series levels. Collection-level criteria include the significance of a scientist's career and the uniqueness, coverage, and accessibility of the manuscripts. Series frequently found among medically related manuscripts are enumerated and discussed. Types of organizational records and the desirability of accessioning them along with manuscripts are considered. Advantages of direct communication with creators of manuscripts are described. The initial appraisal process is not the last word: reevaluation of materials must take place during processing and can be resumed long afterwards.