interpret the results of others". An admirable objective. However, if the resultant volume is to be of value to its declared audience, the author will need to have clear in his mind the needs of that audience.

This volume is divided into seven articles : Vacuum Physics; Photography and Optical Instruments ; Interference and Polarisation ; Microscopy; Radiography; Diffraction; Spectroscopy. The article on spectroscopy is typical. I t begins: "If white light is passed through a prism or a diffraction grating, it will be dispersed into its constituent colours. The spectrum formed is a continuous spectrum since it is a continuous band of colour spreading from violet through to red . . ." This should come as no surprise to any potential reader. However, from such a gentle, pre-O-level start, within the next three pages, the reader is supposed to have digested black body radiation, band spectra, line spectra, emission spectra (both arc and spark), ultraviolet spectra, infrared spectra and ultraviolet fluorescence spectra. By the end of the article virtually every form of spectro- scopy has been mentioned but always in vague generalities. This might be tolerable if there were adequate compensation in the way in which the practical aspects are dealt with. But this is not so.

The balance between what is laboured and what is skimped is different for every article but one way or another each article resembles a badly made custard-thin and watery with lumps in it. It is difficult to imagine who could benefit from this book and, regrettably, it must be assigned to that select band of five-star shunnable books.

D. Neylan

WE MUST LEARN TO WALK BEFORE WE CAN RUN

Information Systems B. C. Vickery (Butterworths, London, 1973; 345@., index, A6.00)

One of the most experienced workers in the field has made a detailed study of specialized information systems which are mainly based on documents.

An analysis of retrieval subsystems is presented with reviews of the various models used, separate chapters being devoted to features of design and evalua- tion.

The final pages give some indication of the author's inclination towards the useful areas of work in the investigation of "the infant of information science".

I feel that the practice of showing the relevant important citations as part of the index is to be commended.

Michael Swain

MEASURING THE INS AND OUTS

Principles of Biological Regulation: an Introduction to Feedback Mechanisms Richard W. Jones (Academic Press, New York and London, 1973; 359PP., A7.50)

This book is an introduction, at undergraduate and research student level, to physiological modelling. The treatment-largely pictorial and needing only basic mathematics-is of the fluxes of materials, energy and information which act as signals to maintain an organism's status quo ("homoeostatus quo", one might be tempted to say).

There are irritations. Some rather ponderous statements are unnecessary: we do not need telling (p.331) that the Law of Conservation of Mass applies to biochemical reactions. Other ideas should have been expanded: the bald statement (p.7) that there is a difference between equilibrium and steady state, and that the former is equivalent to biological death, looks distinctly odd at first sight but could (and should) have been explained in terms of, say, reaction kinetics. Generally, however, the material is well presented and moves easily