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Academia and the Profession |

Medical Resources on the Internet

Jerry V. Glowniak
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From the Veterans Administration Medical Center, Portland, Oregon. Requests for Reprints: Jerry V. Glowniak, MD, Veterans Administration Medical Center RF 115, PO Box 1034, Portland, OR 97207.

Copyright ©2004 by the American College of Physicians

Ann Intern Med. 1995;123(2):123-131. doi:10.7326/0003-4819-123-2-199507150-00008
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Advances in telecommunications technology in the last decade have fostered the development of computer networks that allow access to vast amounts of information and services.Of the many computer networks that have been developed, the most prominent is the Internet. Originally intended to be a way to share computing resources among academic and research institutions in the United States, the Internet has gradually evolved into a worldwide network of computers that provides various services reflecting the eclectic nature of its component networks. The recent upsurge in interest in the Internet is due to several mutually reinforcing factors: increased ease and availability of access to the Internet, lower access charges, faster communications, and more organizations offering commercial and noncommercial services over the Internet.

Of particular interest to the medical community is the large and increasing number of technical, scientific, and biomedical resources that can be accessed through the Internet.Most large medical centers have publicly accessible information, and some large organizations, such as the National Institutes of Health, have extensive databases and services that can be used by medical researchers, clinicians, and educators. In addition, many medical organizations and some medical journals are advertising their services over the Internet and can be contacted through electronic mail.

As the cost of telecommunications decreases and the speed of telecommunications increases, new forms of computer communication, such as long-distance, real-time audio, and video services will become available. Computer networks in general and the Internet in particular are likely to play more important roles in many aspects of medicine in the future.


internet ; computers


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Figure 1.
The principal National Science Foundation network (NSFNET) in the United States.

The structure for ANSNET (Advanced Network and Services network), the major high-speed Internet network in the United States through the end of 1994, is shown. Because most of the funding for this network came from the National Science Foundation, the network was usually referred to as NSFNET. The links in the network are fiberoptic cables leased from MCI that can transmit 45 millions bits of information, equivalent to 1000 pages of text, per second. In 1995, NSFNET stopped funding ANSNET. Currently, most of the long-distance Internet service in the United States is provided by telecommunications companies, such as Sprint and MCI.

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Figure 2.
Naming and numbering scheme for Internet computers.

A computer at M.D. Anderson Cancer Center in Texas that can be reached by gopher is used as an example. Computer names are strings of characters separated by periods. The leftmost string is called the host name, and succeeding strings identify subnetworks, the network, and the top-level domain to which a computer belongs. A computer name may have several or no subnetwork names. Each computer name has an associated Internet Protocol address consisting of four numbers, each in the range 0 to 255, separated by periods. Depending on the type of network, the leftmost one to three numbers identify the network, and the remaining numbers identify the computer (the host).

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Figure 3.
Components of a Uniform Resource Locator (URL).

World Wide Web browsers use this format to locate documents. The leftmost set of characters identifies the mode of access. For the World Wide Web, the access method is the hypertext transport protocol (http). Other common access methods are telnet, FTP [file transfer protocol], and gopher. A colon and two forward slashes follow the access method. The next entries are 1) a computer name; 2) the directories that lead to the document, with entries separated by forward slashes; and 3) the name of the document or file. If the directory path and file name are omitted, as in the second example, the main menu or Web page at the site is displayed.

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