Bulbring and Whitteridge [1945] have shown that their activity is not affected

Transcription

1 THE ACTIVITY OF PULMONARY STRETCH RECEPTORS DURING CONGESTION OF THE LUNGS. By R. MARSHALL and J. G. WIDDICOMBE. From the Department of Physiology and the Dunn Laboratory, The Medical College of St. Bartholomew's Hospital, E.C. 1. (Received for publication 13th November 1957) The effect of pulmonary congestion on the activity of "slowly adapting" pulmonary stretch receptors has been investigated in cats with closed chests. During positive pressure inflation of the lungs congestion caused a mean increase in discharge rate of about 20 per cent at any volume; this was more uniform with large inflations. A similar sensitization was seen when cats were breathing spontaneously or by means of a phrenic stimulator, and in spontaneously breathing cats the Hering-Breuer inflation reflex was enhanced. The receptors probably lie in the walls of the air-passages, and congestion will increase the degree of stretch of these walls, since alveolar compliance is reduced with a greater pull on the airways. The reasons why previous workers have had negative results is discussed, together with the possible r6le of pulmonary stretch receptors in the respiratory changes caused by pulmonary congestion. RECENT work on pulmonary stretch endings indicates that they do not behave as straightforward lung volume receptors, as believed by Adrian [1933]. Although their primary stimulus is the volume of the lungs, their response at any lung volume is influenced by bronchial tone [Widdicombe, 1954], by transthoracic pressure [Weidmann and Bucher, 1951] and by the previous history of the lung [Davis, Fowler and Lambert, 1956]; on the other hand Bulbring and Whitteridge [1945] have shown that their activity is not affected by vascular congestion in perfused cats' lungs. This last result is surprising, both on theoretical grounds and in the light of the recent work mentioned above, although it is not easy to interpret in the absence of definite evidence for the site of the end-organs. In the cat, the pleura has been eliminated, and indirect evidence suggests that many of the end-organs lie in the air passages rather than the alveoli [Davis et al., 1956: Widdicombe, 1954]. In either site they should be affected by the degree of pulmonary congestion. In the alveolar wall there would be a close relationship between capillary diameter and the shape of an end-organ, while pulmonary congestion should influence bronchiolar and bronchial mechano-receptors in so far as changes in the mechanical properties of the alveoli would alter gas volumes and mural tensions in the air passages. To investigate this problem further we have repeated the experiments of Bulbring and Whitteridge in cats with closed chests. METHODS Each cat was ansesthetized with pentobarbitone sodium (32 mg./kg.) intraperitoneally, and tracheal and venous cannuloe inserted. The animal's chest was opened on the left between two ribs during artificial ventilation of the lungs. The pericardium was opened and the cat heparinized (10 mg./kg.). A balloon (up to 2 x 3 cm. when 320

2 Pulmonary Congestion and Lung Receptors 321 distended) attached to polyethylene tubing was tied into the left atrium, and a polyethylene cannula for recording left atrial pressure was inserted on the pulmonary side of the balloon. On distension of the balloon the tip of the cannula probably lay in one of the pulmonary veins. The chest was closed after inserting a third cannula into the intrapleural space; this tube was used to empty the space and to record intrapleural pressure. After closure of the chest the cat breathed spontaneously. An alternative method for causing pulmonary congestion was to put a thread round the aorta; on tightening the thread through a polyethylene tube the vessel was constricted. Distension of the balloon with 1-5 ml. of water raised the left atrial pressure to cm. H20, and for any given balloon volume the level was reproducible. Pressure was never maintained for more than 2 min., and was usually restricted to 0 5 min. to lessen the risk of pulmonary cedema. The latter was never seen. Constriction of the aorta caused larger changes in left atrial pressure (up to 80 cm. H20) and a profound fall in systemic blood pressure. Since reproducible and moderate changes could not be obtained by this latter method it was only used in five cats. In these a similar loop was put round the pulmonary artery to compare the effects of vascular obstruction with and without pulmonary congestion during spontaneous breathing. It was not used while recording activity in pulmonary stretch fibres. Left atrial, intrapleural and, in some cats, femoral arterial pressures were measured by capacitance manometers attached to saline-filled cannulhe. The frequency responses of the units with cannulae attached were cycles/sec. Intratracheal pressures were measured with an air-filled capacitance manometer with a considerably better frequency response. Tidal volumes were usually measured by integrating the electrical output of a gauze-screen differential-pressure pneumotachygraph; this was similar to but proportionately smaller than that described by Lilly [1950] for man. Since the integrating circuit had a time constant of 40 sec. it was unsuitable for measuring small (0-10 ml.) changes in functional residual capacity. In some experiments, therefore, tidal volume was measured by attaching the tracheal cannula to a air reservoir in which the pressure changes were measured with a capacitance manometer. These pressure changes were always less than 1 cm. H20. Action potentials in single active nerve fibres of the right cervical vagus were recorded by dissecting small strands from the nerve trunks and placing them on saline-wick electrodes. The left vagus nerve was not used since the left lung might be damaged by the thoracic operation. A conventional R.C. amplifier was used with cathode-ray tube and camera. The response of pulmonary stretch receptors to positive pressure inflations was followed either by ventilating the lungs with a constant volume respiration pump, the cat being slightly hyperventilated to inhibit spontaneous respiration, or by arresting the pump and inflating the lungs with a syringe. The latter method allowed lung-volume/discharge-frequency curves to be drawn. Impulse frequencies were measured at the peak pressure on pump inflation, and 1 sec. after completion of a volume change on syringe inflation. Negative pressure inflations of the lungs were achieved either by allowing spontaneous respiration or by using a phrenic stimulator. This was of conventional design for clinical use, and its output was connected to the uppermost roots of the phrenic nerves on both sides using silver electrodes. The cats were slightly overventilated. The tidal volumes usually progressively decreased during phrenic stimulation at constant strength. The Hering-Breuer inflation reflex was investigated in spontaneously breathing cats by inflating the lungs with a known volume of air ( ml.). The intrapleural pressure record indicated the length of inhibition of breathing, and this was expressed as a ratio of the respiratory interval during the control period before inflation. This arbitrary index was reproducible under uniform experimental conditions [May and Widdicombe, 1954]. The cervical vagi were cooled by placing them on silver "thermodes" through which cooled alcohol was circulated; the apparatus was similar to that described by Dawes, Mott and Widdicombe [1951].

3 322 Marshall and Widdicombe RESULTS The easiest way to investigate the effect of pulmonary congestion on stretch receptor activity is to ventilate the lungs with a constant volume pump and to record changes in peak discharge rate at different pulmonary vascular pressures. This was the method used by Biilbring and Whitteridge [1945] on perfused lungs. We found that in cats with closed chests distension of a balloon in the left atrium caused maintained and reproducible rises in pulmonary venous pressure to cm. H20. Eight receptors were investigated in this way (Table I) one of which is illustrated in fig. 1. Although all the TABLE I.-THE EFFECT OF PULMONARY VASCULAR CONGESTION ON THE PEAK FREQUENCY OF DISCHARGE OF STRETCH RECEPTORS STIMULATED BY CONSTANT VOLUME (30-50 ML.) INFLATIONS OF THE LUNGS WITH A RESPIRATION PUMP. THE RESIULTS ARE AVERAGES OF FIVE ESTIMATIONS BEFORE, DURING AND AFTER CONGESTION (TOTAL FIFTEEN). STANDARD ERRORS OF THE MEANS ARE GIVEN. THE SIGNIFICANCES OF THE CHANGES IN IMPULSE FREQUENCY CORRECTED FOR A 5 ML. INCREASE IN FUNCTIONAL RESIDUAL CAPACITY ARE GIVEN. Peak frequency of discharge (impulses/sec.) andofefore During dange corrected for P Receptor Before Change Change Significance and after congestion durion 5 ml. rise in congestion congestion volume 1 125± ± < ±1d7 148± < ± < ± ± < ±1.7 79±1* < ± ± < ±1t ±1.4 20± end-organs showed increased discharge on pulmonary congestion, this could have been due to an increase in functional residual capacity. Since the functional residual capacity was not increased by more than 5 ml. when the left atrium was obstructed during spontaneous breathing (range 0-48 ml., in four cats during fourteen periods of congestion; these values agree closely with those of Bulbring and Whitteridge) and occasionally by up to 10 ml. when the aorta was constricted (range ml. in two cats, four periods of congestion), it seemed unlikely that the increases in discharge were due to uniform rises in lung volume. For six receptors in Table I correction has been made assuming an increase in functional residual capacity of 5 ml. From the volume/discharge curves of these endings (see below) the rise in discharge frequency corresponding to a 5 ml. increase in lung volume was measured and subtracted from the rise in frequency due to congestion. Of these receptors four showed significant (P < 0-01) increase in impulse frequency after this correction had been made. It remained possible, however, that there was a change in the distribution of gas in the lungs, and that the receptors lay in pulmonary units which were relatively overdistended.

4 Pulmonary Congestion and Lung Receptors A more thorough method of analyzing receptor activity was used in plotting volume/discharge frequency curves before and during pulmonary congestion over a wide range of volumes. Inflations were made with a syringe, and eighteen receptors were examined. Fig. 2 shows a record from one endorgan, and fig. 3 illustrates responses from three receptors. Thirteen endings were unequivocally sensitized throughout the range of inflations (fig. 3, C), although in five of these the change was relatively small, under 15 per cent increase in impulse frequency (B). Sometimes the effect was greatest at L.A.PITP. 1.1? ~~~Icm.H LA.F? ~~~~~ see. ~ A cm.h so 1 ~~~~~~~~~~~~~ B C FIG. 1.-Effect of pulmonary vascular congestion on a pulmonary stretch receptor during phasic positive pressure ventilation from a pump (40 ml.). Uppermost trace: action potentials in a single vagal fibre. Middle trace: left atrial pressure (positive downwards). Lowest trace: intratracheal pressure (positive downwards). A, before; B, during and C, after pulmonary congestion. During congestion there is a greater peak frequency, and the receptor fires during expiration. Action potentials retouched. large volumes, sometimes at small. Three receptors showed an increased discharge with larger inflations but a slight effect or no change with small inflations (A). One receptor had a decreased discharge at all levels of inflation and one was not measurably affected by congestion. In an attempt to express these results quantitatively Table II has been prepared, which shows the change in discharge frequency at small and at large inflation volumes. It will be seen that in the former instance there is a slightly smaller mean change with rather greater variation than with large volumes. With both volume ranges the mean difference in discharge frequency is significantly above zero (P < 0O01). In determining the significance of the change in impulse frequency corrections should be made for the increases in functional residual capacity caused by congestion. However it proved impossible to measure these accurately during inflations of the lungs with a syringe. We

5 324 Marshall and Widdiconmbe have, therefore, once again assumed that the functional residual capacity might have increased by 5 ml. (the greatest increase seen when congestion was caused by left atrial obstruction). On this basis the figures in Table II have been corrected. Since the values for "large inflations" were one step below the maximum inflation, this has involved interpolation but not extrapolation of the curves. From these results it seems that even an increase in functional residual capacity of 5 ml. would not account for the sensitization TABLE II.-THE EFFECT OF PULMONARY VASCULAR CONGESTION ON THE FREQUENCY OF DISCHARGE (MEASURED 1 SEC. AFTER EACH INFLATION) OF STRETCH RECEPTORS STIMULATED BY INFLATIONS OF THE LUNG WITH A SYRINGE. STANDARD ERRORS OF THE MEANS ARE GIVEN FOR THE CHANGES IN DISCHARGE FREQUENCY. LARGE INFLATIONS ARE ONE INFLATION STEP LESS THAN THE MAXIMUM VOLUME FOR ANY GIVEN CAT ( ML.); SMALL INFLATIONS ARE ABOUT ONE-THIRD OF THIS (20-50 ML.). RESULTS CORRECTED FOR AN INCREASE IN FUNCTIONAL RESIDUAL CAPACITY OF 5 ML. ARE INCLUDED. Small inflations Large inflations Receptor and after Change during Corrected and after Change during Corrected congestion condestter congestion change congeto angestion congestion change (impulses/sec.) (impulsessec) (impulses/sec.) (impulses/sec.) (impulses/sec.) (impulses/sec.) Means ± ± ±2-6 Significance (P) < 0 01 < < 001 < 0 01 obtained. In Table II standard errors of the means are not included for individual receptors, since usually only one or two inflations with a syringe were done during congestion for each end-organ. However each inflation included measurements at five to six intermediate volumes, as shown in figs. 2 and 3. We have tried to discover if pulmonary stretch receptor activity was influenced by pulmonary congestion during spontaneous respiration. This is difficult to do since the tidal volume is altered, and only if the tidal volume is unchanged or reduced and the receptor discharge is increased by congestion can a sensitization be claimed. Of five receptors investigated three behaved in this way, the other two being equivocal. However the cats breathed more rapidly as well as more shallowly, and it is possible that a quick inflation

6 A LAP cm.h I 1.1:1 *- li* I1 il 11 nnril"fu ii n rmim I I sec. I- r~~~~~~~~~~~~~~~i- -li ~F a! 1 w a'i mi Hi 11 A1 ON1 0i ot. 11 la HOHN H it H lo! M? li 111 i *I 101 HI HNINIIIHIMMMom IlloilimlommiHol No! IN" I.Tp cm.h20 I II 101 I j IL 11 II ILI III 1-1 III III II -1 i I. 1-1 II I. II III III II III of I, III II LII.- Il IIIII.I I 6 If 1- I I r -1-1 III-[, r ---I rr'.1 IIIIII I-n-F I-[ II-] II IT II 1-1 inh* B A Im I W10 1,11,1111"I I" 1,11, III,I.d.,!II.,I.,..I III ITI 0, kw FIG. 2.-Sensitization of a pulmonary stretch receptor by pulmonary congestion. The lungs were inflated with a syringe in steps of ml. total. Traces as in fig. 1. A, before congestion; B, during congestion. Action potentials retouched. [ 15O a Congested Control A - to a n &i 100 Congested u c Control C InflatIon Volume (ml.) FIG. 3.-Inflation-volume/discharge-frequency curves for three receptors, before and during pulmonary vascular congestion.

7 326 Marshall and Widdicombe would produce as great a peak frequency as a slower inflation to a larger volume, since the receptors (although "slowly adapting") have a significant adaptation to constant volume inflations. The use of a phrenic stimulator should obviate this objection, but for technical reasons we found it difficult to apply. Only two receptors were successfully investigated, and both gave greater peak frequencies (increases of 6 and 13 per cent) on lung congestion although the tidal volumes and rates of inflation were reduced. These few results with spontaneous and phrenic stimulated breathing are not, therefore, inconsistent with those using positive pressure inflations. Of the twenty-two receptors included in Tables I and II, five were spontaneously firing at expiratory level, and congestion caused an increased discharge from all these endings during this phase (range 6-66 per cent; mean 25 per cent). Three other receptors, silent during control expiratory pauses became active at this phase on congestion (e.g. figs. 1 and 2). Examination of the pressure/volume curves for these endings suggested that the sensitization was probably not due to an increase in functional residual capacity. If pulmonary stretch receptors are sensitized by congestion of the lungs one would expect the Hering-Breuer inflation reflex, mediated by these receptors, to be enhanced. This reflex can be recorded as the period of inhibition of breathing produced by inflation of the lungs. However pulmonary congestion increases respiratory drive and thus sets a new level of activity in the respiratory centres, so that even if the inhibition is shorter there may be sensitization of the reflex. In five cats breathing spontaneously the lungs were inflated with a known volume of air and the length of the respiratory inhibition measured and expressed as a ratio of the previous respiratory interval. In four of these cats the ratio was consistently increased by congestion caused by obstruction of the aorta, often with an absolute increase in the time of inhibition (fig. 4). In an attempt to discover how the respiratory changes caused by congestion of the lungs were influenced by pulmonary stretch receptors, in three of these five cats the vagi were cooled to 8-10 C. and the lungs congested. At this temperature fibres from the pulmonary stretch receptors are blocked while other vagal afferent nerve fibres continue to conduct [Dawes et al., 1951]. With the vagi cooled rapid shallow respiration was not seen, although respiratory stimulation was clearly present, the cats usually making long and powerful inspiratory efforts (fig. 5). DISCUSSION Our results show that congestion of the lungs sensitizes stretch receptors when they are stimulated by positive pressure inflations from a pump or syringe, and that this cannot be explained by an increase in functional residual capacity. More reliance is to be placed on the results with inflations with a syringe, since pulmonary stretch receptors are influenced by the rate of inflations [Davis et al., 1956] as well as by lung volume. Using a syringe, discharge rates were measured 1 sec. after inflation was complete, i.e.

8 Pulmonary Congestion and Lung Receptors under nearly static conditions. Some end-organs gave far higher frequencies when stimulated by pump inflations of ml. than when equivalent volumes of air were injected by a syringe. This is due to the receptors responding to the active phase of inflation as well as to the maintained inflation. It is I.P P. LT.P B E FIG. 4.-Changes in the Hering-Breuer inflation reflex caused by constriction of the aorta (B) and constriction of the pulrnonary artery (C). A is a control. Upper trace, intratracheal pressure (positive downwards). Lower trace, intrapleural pressure (positive downwards). The length of respiratory inhibition is indicated by the two arrows on each record. In B, although there is stimulation of breathing caused by the aortic obstruction, there is a longer inhibitory pause. In C there is also respiratory stimulation, but no potentiation of the reflex. The inhibitory ratios (see text) for the three records are 300, 455 and 253 per cent respectively. L.A.P? cm H20 TV. T.V. -50 A ml ] Lvpcn.Ho 50 IPP~~~.0 B FIG. 5.-Effect of pulmonary congestion on respiration in a cat with vagi intact (A) and with vagi cooled to 8 C. (B). With the vagi cooled there is no rapid shallow breathing, but prolonged inspirations are present. Uppermost trace: left atrial pressure (positive downwards). Middle trace: tidal volume (inspiration upwards). Lowest trace: intrapleural pressure (positive downwards). Congestion is started at the arrows. unlikely that the rises in discharge rate on congestion were due to increase in functional residual capacity. The results remained statistically significant even assuming an increased volume of 5 ml., and the mean increase in lung volume which would cause equivalent increases in discharge frequency was over 20 ml. At first sight these results seem to contradict those of Bulbring and

9 328 Marshall and Widdicombe Whitteridge [1945] who used a perfused lung preparation. However in Table II it will be seen that with moderate volumes of inflation three receptors showed a decreased rate of discharge on congestion of the lungs, and that the mean increase is considerably influenced by four receptors (5, 17, 18 and 19) which were greatly sensitized. Apart from these four our results at this level of inflation are similar to those of Bulbring and Whitteridge in giving a variable response which might be explained, as they suggest, by unequal ventilation of pulmonary units consequent to vascular congestion. With large volumes, however, we found a more consistent sensitization and the mean increase was greater than that at smaller volumes. With the larger inflations the effect of unequal ventilation would be minimized, although these inflations (with trans-pulmonary pressures of cm. H20) would be well within the vital capacity of the cat. In preparations of perfused lungs one might expect greater distributional inequality of ventilation than in animals with closed chests; and if the lungs were allowed to collapse between inflations this would both reduce the functional residual capacity and increase the number of poorly ventilated pulmonary units. We therefore think that our results are compatible with those of Bulbring and Whitteridge, but that by working under more physiological conditions and by using a greater range of inflations the sensitization of pulmonary stretch receptors by congestion of the lungs has become apparent. The sensitization of the end-organs is presumably due to the greater stretching of the air passages when the compliance of the alveoli is reduced. This assumes that the airways are the site of the receptors [Widdicombe, 1954; Davis et al., 1956]. The fact that the change in impulse frequency was not greater must rule out the alveoli as their localization, which is in any event unlikely since they do not often adopt a cardiac rhythm. It is most unlikely that alveolar receptors would only change their discharge rate by 20 per cent when pulmonary capillary pressure rises to 40 cm. H20. The variability of our results is probably due to two factors; left atrial pressure was not raised to the same value in each experiment, and end-organs in different parts of the airways would show quantitatively different responses according to their exact site. In the cat, pulmonary congestion causes only a small decrease in compliance whether the chest is open or closed [Hughes, May and Widdicombe, 1958]; raising the left atrial pressure to cm. H20 decreased static compliance by less than 10 per cent in the majority of experiments and this may explain the small size of the sensitization seen. The extent to which the sensitization may influence the respiratory response to congestion is difficult to assess. The few experiments with spontaneous and phrenic stimulated breathing suggest that receptors are also sensitized under these conditions. It is probable that the Hering-Breuer inflation reflex is enhanced by congestion of the lungs, but the absence of a satisfactory method of measuring the potency of the reflex under conditions of changing activity in the respiratory centres makes this conclusion tentative. With the vagi cooled to block the afferent nerve fibres from the stretch receptors, pulmonary engorgement caused maintained inspiratory efforts

10 Pulmonary Congestion and Lung Receptors 329 rather than rapid shallow breathing, so the role of sensitized end-organs may be to convert the former pattern to the latter. This would be expected from their physiology. Whitteridge and Bulbring [1944] have shown that sensitization of pulmonary stretch receptors by volatile anaesthetics produces rapid shallow breathing. In their experiments a sensitization of per cent or even more only reduced tidal volume by 50 per cent, so a sensitization of 20 per cent by pulmonary congestion should exert a far smaller effect. There has, however, been little quantitative work on the effect of impulses from pulmonary stretch receptors on the respiratory cycle. There is good evidence that congestion of the lungs influences respiration by afferent pathways other than that of the stretch fibres (see Whitteridge [1950]; Aviado and Schmidt [1956], for references). In our experiments respiratory stimulation was produced by pulmonary congestion when the stretch fibres were blocked, and there was also evidence that back pressure effects proximal to the lungs contributed to the respiratory changes in the intact animal (e.g. fig. 4, C). Therefore although our results support Christie's [1938] view that increased stiffness of the lungs should sensitize pulmonary stretch receptors, we have no wish to revive the theory that this sensitization is responsible for the dyspncea and rapid breathing of clinical pulmonary congestion; it is merely thought that increased activity from these endings may be one factor in the altered breathing caused by congestion of the lungs. A further reason for caution is the danger of transferring results from one species to another, especially since there is evidence that the Hering-Breuer reflexes are very poorly developed in man compared with the cat and other species [Marshall and Widdicombe, 1958]. ACKNOWLEDGMENTS We are grateful to Professor D. Whitteridge, F.R.S., for his helpful criticism of the manuscript. Part of the apparatus used was bought with a grant from the Central Research Fund, University of London. REFERENCES ADRIAN, E. D. (1933). "Afferent impulses in the vagus and their effect on respiration", J. Physiol. 79, AVIADo, E. M. and SCHMIDT, C. F. (1956). "Reflexes from stretch receptors in blood vessels, heart and lungs", Physiol. Rev. 35, BtLBRING, E. and WHITTERIDGE, D. (1945). "The activity of vagal stretch endings during congestion in perfused lungs", J. Physiol. 103, CHRISTIE, R. V. (1938). "Dyspncea; a review", Quart. J. Med. 31, DAVIS, H. L., FOWLER, W. S. and LAMBERT, E. H. (1956). "Effect of volume and rate of inflation and deflation on transpulmonary pressure and response of pulmonary stretch receptors", Amer. J. Physiol. 187, DAWES, G. S., MOTT, J. C. and WIDDICOMBE, J. G. (1951). "Respiratory and cardiovascular reflexes from the heart and lungs", J. Physiol. 115,

11 330 Marshall and Widdicombe HUGHES, R., MAY, A. J. and WIDDICOMBE, J. G. (1958). "The effect of pulmonary congestion and cedema on lung compliance", J. Physiol. [In the press.] LILLY, J. C. (1950). "Flowmeter for recording respiratory flow of human subjects." In Methods in Medical Research, 2, , ed. Comroe, J. C. Chicago: Year Book. MARSHALL, R. and WIDDICOMBE, J. G. (1958). "The weakness of the Hering-Breuer reflexes in man", J. Physiol. 140, 36P. MAY, A. J. and WIDDICOMBE, J. G. (1954). "Depression of the cough reflex by pentobarbitone and some opium derivatives", Brit. J. Pharm. 9, WEIDMANN, H. and BUCHER, K. (1951). "Zur Frage der Spezifitiit der vagalen Dehnungreceptoren in der Lunge", Helv. physiol. acta, 9, WHITTERIDGE, D. (1950). "Multiple embolism of the lung and rapid shallow respiration", Physiol. Rev. 30, WHITTERIDGE, D. and BtLBRING, E. (1944). "Changes in activity of pulmonary receptors in anmesthesia and their influence on respiratory behaviour ", J. Pharmacol. 81, WIDDICOMBE, J. G. (1954). "The site of pulmonary stretch receptors in the cat", J. Physiol. 125, BOOK REVIEWS THE CLINICAL APPLICATION OF HORMONE ASSAY. By J. A. LORAINE. Edinburgh and London: E. & S. Livingstone, Ltd Pp. xii s. This book is really about "Hormone Assays for Clinical Application". Its main contribution is a much-needed review of most of the clinically applicable assays of urinary or blood hormonal level. Dr. Loraine gives a readable outline of this developing subject, and without wearisome details makes clear the limitations and potentialities of the methods. He is particularly at home, of course, in expounding the Edinburgh views, and in recounting the experiments and the clinical experience gained with these methods at the Edinburgh Clinical Endocrinology Research Unit. The book is particularly useful for its chapters covering the assay methods recently studied and often developed there; especially the assays of urinary gonadotrophins, cestrogens, pregnanediol, and also of adrenaline and noradrenaline. The introductory chapter is on the requirements for a satisfactory bioassay, and on the criteria for determining the accuracy, precision, specificity and sensitivity of any assay. Previous investigators have not always followed these precepts, as the reader is rather frequently reminded in the rest of the book. Many readers might have liked all the normal values for the recommended assays assembled together, perhaps at the end of this introductory chapter. Then follows a series of chapters on the various hormones which have been assayed in human blood and urine. The assays of established clinical validity and value, such as those of the pituitary gonadotrophins, chorionic gonadotrophin, cestrogens, pregnanediol, corticosteroids, 17-ketosteroids, and adrenaline and noradrenalin might well have been segregated into a separate section of the book. But they appear seriatim along with others of potential clinical value such as the thyrotrophin and insulin assays, and others still needing development before they can reach this stage-i.e. ACTH, prolactin, growth hormone and antidiuretic hormone. Each chapter first covers the methods of extraction and then those of the assay, finally reviewing the normal values found, and then the findings in various disease