Histology Time on CD.

Histology Time on CD replaces Histology: A Photographic Atlas, a videodisc and barcode manual distributed with accompanying software and commonly referred to as Histology Time [1]. Histology Time on CD contains more than 5,000 light microscope images organized into nineteen chapters covering cytology, tissue types, and organ systems. Within each chapter, a series of histological images is available for study in one of four modes: Micro Lab, described in more detail below; Quiz Time, a series of image-based identification questions; MC exam, a series of multiple choice questions not based on images; and K exam, a series of K-type questions also not image-based. The practice questions are short, non-vignette type questions having to do with identification of structure or with simple structure-function relationships. Practice questions are delivered in random order each time questions are accessed. Items can be flagged, and a subset of questions generated for repeated review.

Micro Lab mode explores the material in a didactic format, providing descriptions and explanations of images within the relevant topic. Each chapter begins with a plate or two of images representing the main topics in the chapter and a textbox giving an overview. A GoTo button offers a table of contents for the chapter and allows users to select subtopics, which may have further subtopics, to explore. Each topic or subtopic is introduced with an image of cells, tissues, or both with an accompanying brief description of the material in a textbox and an Examples button that provides multiple illustrations of the particular cell or tissue being described. The number of examples of each item ranges from one to nineteen and averages about ten. Labeling of the images is sparse: topic images have the main features labeled and the Examples images are unlabelled or have the item in question indicated with an arrow. For example, the epithelium chapter in Micro Lab mode begins with two introductory plates, one showing different types of simple epithelia and the other showing different types of stratified epithelia. Under the simple epithelium heading, the GoTo button offers simple squamous, simple cuboidal, simple columnar, and pseudostratified columnar as subtopics. Choosing the simple cuboidal subtopic takes users to a micrograph showing a section of intestine with the mesothelium indicated by brackets. The accompanying textbox explains the function of simple squamous epithelia and the usual settings in which it is found. The Examples button provides fifteen more micrographs illustrating simple squamous epithelia in whole mounts or in sections (mostly the latter).

Depth of coverage and level of detail are considerably less than that of Wheater's Functional Histology [2] and Color Atlas of Histology [3], two popular atlases used in medical histology courses [4]. This coverage is in keeping with the orientation of the program, which is very visual with scant textual explanations. Some examples of the level of detail follow: In the connective tissue chapter, type I collagen is described simply as collagen; that reticular fibers (illustrated with silver stain) are type III collagen and that cartilage contains type II collagen are mentioned, but brown fat is not mentioned. In the cartilage chapter, chondrocytes are illustrated, but chondroblasts are not mentioned. In the bone chapter, osteocytes, osteoblasts, and osteoclasts are illustrated, but woven bone is not mentioned. In the central nervous system section, microglia are illustrated (Golgi stain), but other glial cells are not mentioned. For the most part, the material is straightforward basic histology, although there are occasional brief clinical references in the Micro Lab textboxes or in the multiple choice questions.

The images are mostly of hematoxylin- and eosin-stained sections but also include some material stained to highlight specific features, such as connective tissue fibers, and some whole mounted (mesentery) and smear (blood, bone marrow, nerve) preparations. Information about magnification is not given. Image quality varies from poor to excellent and is usually quite good. Image labels and textual information are generally free of error. A notable exception is in the multiple choice questions in the digestive system chapter. These appear to have been incorrectly keyed, as more than half of the indicated answers are wrong. The author is aware of this problem and is taking steps to correct it. (Editor's note: The author reports that version 1.1 corrects this problem and is now available.)

The great strength of this program is the large number of images combined with well-designed study and self-testing modes that allow students to study and review material they are learning in a histology course, especially the laboratory portion. With more than 5,000 images, Histology Time on CD is far ahead of the many other histology CDs now available, most of which have fewer than 1,000 images. The University of Arizona College of Medicine has had the earlier videodisc version of the program available for medical students since 1993, and it has been heavily used as a study tool. Some students use it as a replacement for laboratory experience, though we discourage this. Although having only a third of the images, the CD version is not conspicuously reduced in scope, and it is likely to be equally popular.

Some areas in the program could be made even more useful to students. First, a little more detail in labeling of images in the Micro Lab mode or more explanation of the images using textboxes would be helpful along with ballpark magnification information (low, medium, and high). Choice of magnification to illustrate particular items, especially for the Quiz Time images, could be improved. Currently, for a number of items, the magnification is either too high or too low for students to be reasonably expected to identify the item. A greater diversity of test questions in all three modes would make the practice tests much stronger review tools. As it is, there is sometimes a monotonous degree of repetition, although some students may appreciate it. A back button allowing users to back up in the test questions, a helpful feature in the videodisc version, has been dropped in the CD version. More clinical correlations and some vignette-type questions would better help students prepare for board exams. The single most useful feature that this reviewer would like to see added is a capacity for global testing. As it is now, the program only allows testing within a chapter; selecting another chapter necessarily gives students important cues about what material they are looking at and therefore makes self-testing less effective. Some sort of global index or search function would also be very desirable.

Overall, Histology Time on CD provides a large bank of histological images in readily accessible formats at a reasonable price. It is likely to be a very useful supplement to medical or general histology courses.