The limited supply of blood in the body is normally differentially routed to the various viscera and skeletal muscles as needed by the action of the AND on the sphincter muscles of the arterioles. The vascularization of the skin is under the exclusive control of the sympathetic division of the ANS. To the extent that both divisions of the ANS are represented in the other regions of the body, they function as antagonists. The effect of the sympathetic system is to put blood into skeletal muscle, while the action of the parasympathetic system is to route it into the viscera.

Although there is conflict in the literature over the issue of whether neutral hypnosis produces any change in the peripheral distribution of blood, the evidence seems consistent that hypnotic suggestions can influence the distribution of blood to the skin and other structures. Many of the effects reported on skin temperature, galvanic skin response (GSR), mammary gland development, and the production and alleviation of skin eruptions are probably explainable in terms of alteration of blood flow to these areas (Barber, 1978c). Timney and Barber (1969) replicated earlier findings that subjects in neutral hypnosis developed a significant increase in oral temperature, while Jackson and Hastings (1981) found no significant difference in oral temperature between hypnotic and simulating subjects. In a second study, they found a marginally greater decrease in oral temperature in high-susceptibility female subjects. By imagining that their hands are in cold or hot water, subjects are able to produce temperature differences of up to 20°F between their two hands. Maslach, Marshall, and Zimbardo (1972) have found that while hypnotized subjects were able to change the skin temperature in their two hands in the opposite direction simultaneously, waking controls were unable to do so. Similar effects have been produced using biofeedback. Piedmont (1981) and Crosson (1980) confirmed that skin temperature is alterable by suggestion under hypnosis, and Raynaud and her colleagues (1984) found that neutral hypnosis did not affect rectal or skin temperature, but the suggestion of the sensation of heat decreased rectal temperature and raised mean skin temperature.

McDowell (1953) reported vasodilation in a subject's leg following suggestions of the leg being immersed in warm water, and Nallapa (1952) reported increasing circulation in a case of Buerger's disease (thromboangiitis obliterans) by hypnotic suggestion. Reiter (1956) reported that suggestions of increasing blood flow to the thyroid gland increased the basal metabolism rate (BMR) to 110, resulting in body weight being reduced to normal in an obese patient.

Hypnosis itself does not affect BMR, but emotions produced by hypnotic suggestions may increase or decrease it (Wallis, 1951; Whitehorn et al., 1932). Posthypnotic suggestions have induced body temperature elevation, but Kline (1957, 1958c) believes that direct suggestions are ineffective and that emotive or hallucinatory suggestions are needed. Contrary to Pavlov's theory that hypnosis involved vasoconstriction in the cerebrum, Nygard found no difference in cerebral circulation in waking or hypnotized subjects.

The GSR refers to the electrical resistance of the surface of the skin. Skin resistance is lowered by the activity of the sweat glands, which secrete an electrolyte onto the surface of the skin. Crasilneck and Hall (1959) report conflicting studies concerning the effects of neutral hypnosis and suggestions of anesthesia on GSR. Using six subjects, Barber and Coules (1959) found no change in skin resistance during induction and a gradual increase of resistance throughout the remainder of the experiment, which was punctuated by responses to individual suggestions. Since sweating is a response to stress produced by the sympathetic division of the ANS, it is likely that what happens is a function of an individual subject's reactions to suggestions. If the subject views the induction procedure as a relaxing event, he will probably respond with lowered sweat gland activity and a higher skin resistance. If he is apprehensive, either about the procedure in general or about some specific suggestion, he is likely to sweat more and thus have a lowered skin resistance. Often the subject's subjective feeling that he is about to go into an unusual state of consciousness may be enough to frighten him into producing a sudden change in GSR level.

A large variety of skin conditions appear to be affected by hypnotic suggestions. Congenital ichthyosiform erythroderma, a scalelike eruption, has been improved by hypnotic suggestion, and in some cases, results have been reported that were limited to the specific areas of the body to which suggestions were directed (Mason, 1952; Schneck, 1954). Large nevi and warts have been reported successfully treated by hypnotic suggestion (Asher, 1956; Fernandez, 1955; McDowell, 1949). Asher reported 15 out of 25 susceptible patients cured of warts. Barber (1978b) reported a rapid cure in 3 out of 11 patients, but an attempt to limit a cure to warts on only one hand by suggesting an alteration of the blood supply to the warts and "feeling them tingle and dry up" was unsuccessful. Both hands cleared up.

In 1941, Pattie reviewed the literature on blister formation. In a typical experiment of the time, blister development was attempted by telling a subject that he was being touched with a hot iron. Results were mainly negative, and, since many of the cases reported were poorly documented or controlled, there is conflict in the reports. The issue of whether a blister can be produced is still unresolved, but the weight of the evidence is negative. On occasion, erythema or a welt may be produced in a susceptible subject, and these may have been reported as blisters in some studies.

Johnson and Barber (1976) were unable to produce a blister in 40 subjects, although two developed a localized inflammation. One of these reactions was attributed to self-injury, a problem that Pattie noted in this type of research. Evidently some good subjects are so anxious to produce the effect the hypnotist seeks, they will actually injure themselves to produce it. The researcher must be able to observe subjects constantly or make the skin area in question inaccessible to them from the time of the suggestion until the time of observation of effects. Spanos, McNeil, and Stam (1982) age regressed 17 previously burned subjects to the time of their injuries and suggested that a blister was forming. None showed evidence of blister formation or even skin discoloration, but one did develop an elevated skin temperature at the site of the injury compared to the contralateral site. Barber reports that cold sores can be produced in susceptible subjects by suggestion, and probably even without hypnosis. Ikemi and Nakagawa (1962), using high school students in Japan who were sensitive to a poisonous plant (similar to poison ivy), had both hypnotized and control subjects touch this plant. Both groups were told that it was not the plant they were allergic to. The vast majority of both groups developed no dermatitis. The study was then reversed; both hypnotized and control subjects were instructed to touch a nonpoisonous plant they were told was poisonous. All subjects in both groups developed a dermatitis from slight to marked. Thus, psychological factors have been demonstrated to affect the course of allergic reactions both with and without hypnosis.

A number of studies suggest that breast size may be increased by hypnotic suggestion. Williams (1974), employing controls for weight gain, phase of the menstrual cycle, and measurement position, reported an average increase of 2 inches in bust size in 13 subjects after 12 weekly treatments involving suggestions of warmth, blood flow, tingling, and so on. Home practice sessions were also employed. Willard (1977) replicated this experiment and reported an average gain of 1.5 inches in nine sessions. Staib and Logan (1977) found these gains were retained after 7 months. Erickson (1977b) reported successful hypnotic breast development in a clinical setting.

Respiration rate can be changed by direct or indirect emotion-producing suggestions (Crasilneck and Hall, 1959). Hypnosis per se probably lowers the respiration rate. Reiter (1956) reports that suggestions of pain, anxiety, and grief increase both the depth and frequency of respiration.

Arterial oxygen level is increased by the induction of a pleasant emotion under hypnosis and decreased by the induction of an unpleasant one (Lovett, 1953a, 1953b). Hypnosis per se decreased the waking levels of oxygen saturation. The blood glucose level is closely related to the level of arousal and can be varied by hypnotic suggestion (Barber, 1961b). Olness and Conroy (1985) found that nine out of eleven children between the ages of seven and seventeen were able to increase tissue oxygen in response to taped suggestions. Eight children were experienced in self-hypnosis; three were not. Of the children successful in this task, only one had no previous self-hypnosis training; two children without this training were unable to increase their tissue oxygen.

Hypnosis has often been reported as a treatment for an asthmatic attack (Franklin, 1957; Solovey and Milechnin, 1957; Van Pelt, 1953). Thome and Fisher (1978) found that high- and medium-susceptibility subjects who were given hypnotic suggestions of experiencing an asthmatic attack were convinced that they had experienced one, though physiological measures failed to "'veal a typical asthmatic pattern. Low-susceptibility subjects were unconvinced of the effect.

In a book published in 1953, the same year that Aserinsky and Kleitman published their paper on rapid eye movements (REMs) in sleeping infants that was to revolutionize concepts concerning the stages of sleep and dream research, Weitzenhoffer concluded that hypnosis resembled a stage of light sleep more than either deep sleep or the waking state. In an early article, Barber (1956a) came to the same conclusion. More recent evidence indicates that EEG records obtained during hypnosis are about the same as are obtained in the waking state or in stage 1 sleep (the lightest stage). The EEG record in stage 1 sleep is identical to a waking EEG record except for the appearance of periodic REMs, which is why this stage is sometimes referred to as paradoxical sleep.

No change in a preexisting alpha level is noted on induction (Dynes, 1947). On the other hand, alpha waves were inhibited in nine out of eleven subjects who were given suggestions for visual hallucinations while under deep hypnosis with their eyes closed. Such disruption in an alpha pattern would normally be produced by a subject either thinking or opening his eyes and permitting a visual pattern to stimulate his occipital cortex.

In addition to being capable of producing deep relaxation of the voluntary muscles, hypnosis may be capable of increasing the capability of muscle. Weitzenhoffer (1951) concluded that hypnotic transcendence of voluntary muscular capability is a valid phenomenon. Mead and Roush (1949) noted a significant increase in strength during hypnosis when measured by an arm dynamometer but not when measured with a hand dynamometer. Watkins (1949) suggests that this enhanced muscular ability may be due to the anesthetic effect of hypnosis on pain and fatigue.

Barber and Calverley (1964e), using 60 female volunteers, found that strength of grip was not increased by hypnotic suggestion or by task-motivational instructions. On the other hand, hypnosis per se depressed weight-holding endurance, but task-motivational instructions, with or without a preceding hypnotic induction, increased endurance. In a review of the literature on the subject in 1966, Barber concluded that hypnosis by itself does not increase either strength or endurance, but motivational instructions increase both—with or without hypnosis. Albert and Williams (1975) examined the effects of posthypnotic suggestions on physical endurance. Endurance was found to be lowered with posthypnotic suggestions of fatigue but not increased with facilitating instructions. Nonhypnotized control subjects were not affected by either suggestion. The Borge ratings of perceived exertion indicated that the subjects subjectively perceived the effects suggested subjects, and a control group. When tested posthypnotically, high-susceptibility subjects given motivating suggestions under hypnosis and subjects given waking motivating suggestions performed equally well and better than control subjects. Low-susceptibility subjects given motivational suggestions under hypnosis and subjects exposed to neutral hypnosis did not improve their performance.

Performance on a pursuit rotor task was significantly improved equally by posthypnotic or waking suggestions (Pearson, 1982). Abramson and Heron (1950) found a significant reduction in labor time with hypnotic analgesia during childbirth, suggesting that hypnosis may produce a more effective contraction of the uterine muscles, a more effective cervical dilation, or both.

Neutral hypnosis depresses gastric secretion, while emotion-producing suggestions under hypnosis may alter it in either direction (Crasilneck and Hall, 1959). Suggestions of eating a delicious meal increased gastric acidity and secretion in 34 of 36 subjects. Barber (1965d) makes the point that in most of the studies investigating the physiological effects of hypnosis or hypnotic suggestions, no evaluation was made of the relative effects of the specific suggestions, the positive motivation on the part of the subjects, general suggestions of relaxation, or defining the situation as hypnosis. In cases where these parameters are investigated, he asserts, it is usually found that direct, indirect, or even waking suggestions are effective.

A number of common effects of hypnotic induction were described under the rubric of signs of hypnosis. If conventional methods of Induction, utilizing suggestions of relaxation and sleep are used, these effects commonly include slight to profound muscular relaxation, with consequent alterations in facial expression and posture, eye closure, and lack of spontaneous movement or speech. Other usual concomitants of the hypnotic state Include a literalness and specificity in the understanding of suggestions (mak ing it imperative that the operator carefully phrase suggestions) and in some cases the development of rapport, a condition in which the subject ignores all suggestions except those made by the operator. It is tempting to describe reactions that result from the induction of the hypnotic state per se, or so-called neutral hypnosis, as general responses to distinguish them from those made only in response to specific instructions. This, however, would be mis leading; these reactions, like any other obtained under hypnosis, are most likely made in response to suggestions. In the case of these general responses, the suggestions are being made explicitly or implicitly in the sug gestions used for trance induction. If an individual subject interprets the hypnotist's exhortation to "respond only to the sound of my voice" as meaning the institution of a state of rapport, he will develop one; if not, he will not.

Thus, although the present author agrees with Edmonston (1977b) that re laxation is a common concomitant of hypnosis, he disagrees with his thesis that it is the equivalent of neutral hypnosis. It results simply because of the usual way in which hypnosis is induced—by suggestions of drowsiness and relaxation—and is not essential to hypnosis, as demonstrated by the work of Gibbons (1974, 1976, 1979). The equating of relaxation and neutral hyp nosis is another common misconception and was the reason that Swartz (l982), in a review of the first edition of this book, took exception to the author's statement that, by itself, hypnosis is neither helpful nor harmful, since he (as the author), believes relaxation is valuable in tension-related conditions.

In this section we consider what physiological reactions can bemodified by suggestions, direct or indirect. Responses involving the autonomic nervous system (ANS) are of special interest since such responses are normally not under voluntary control and hence cannot be produced directly. However they can probably be altered by the mediating action of thoughts, ideation, or goal-directed fantasies.

Crasilneck and Hall (1959), Gorton (1949a, 1949b), and Barber (1961) 1965) have reviewed the literature on the physiological effects of hypnosis This literature is often in conflict because of the absence of adequate controls, especially in the earlier studies. Thus several studies have reported a decrease in heart rate in neutral hypnosis, while others have reported a rise. Probably both effects occur. Heart deceleration may result from the relaxation instruc-tions used to induce hypnosis and heart acceleration from the idiosyncratic reactions of subjects to the subjective feelings aroused by trance-induction procedures. If the subject is frightened by the prospect of hypnosis, may increase. Gorton (1949a, 1949b) reports that except for a slight low. due to relaxation, cardiac activity is about the same for subjects under hypnosis as it is when they are awake. Cardiac rate is much lower during sleep than in either hypnosis or waking.

Bauer and McCanne (1980b) found no significant differences in decrease in heart rate, alpha activity, skin conductivity, or respiratory rate between six hypnotized female subjects and six female simulators.

Barber (1961b, 1965d) reports that hypnotized and waking subjects can increase or decrease their heart rate in response to specific suggestions to do so, but hypnosis does not enhance this effect. It is not possible to determine whether direct suggestions to vary the heart rate are effective without the help of mediating ideation because it is not possible to control what the subject is thinking. Since the autonomic nervous system (ANS) is not under direct voluntary control, if heart rate is to be controlled by a subject, it probably must be done indirectly by an emotional response to ideation produced gestions. Barber also points out that alterations in respiration rate, which can be made voluntarily, can affect heart rate. However, it is difficult to distinguish the direct effects of suggestions, if any, from the emotional concomitants of mediating ideation, goal-directed fantasies, or simply relaxation.

Barber cites a study by Van Pelt in which the latter appeals to have pro-duced cardiac acceleration in a calm subject while controlling for the level of adrenaline in the blood. Raginsky (1959) produced a cardiac block for a brief period by hypnotic suggestion. He also produced extra systoles in labile jects (Raginsky, 1953). Linton and colleagues (1977) found no evidence concordance of heart rate between subject and hypnotist based on empathy as some have suggested, but found some concordance during induction. Morgan and coworkers (1976) reported that suggestions of heavy work produced no alteration in cardiac rate in either hypnotized or waking subjects, but they were effective in producing an increase in ventilation. Barber found that in neutral hypnosis, muscle tension, measured by electromyograph (EMG), was significantly lower, but pulse rate was unchanged. Hilgard and colleagues (1974) reported a significant difference in heart rate following sug-gestions of analgesia that was unrelated to the amount of subjective pain reduction but no significant rise in heart rate with hypnotically hallucinated Electrocardiogram changes have been reported following emotion-producing suggestions (Bennett and Scott, 1949; Berman, Simonson, and Heron, 1954) Blood pressure is affected by both cardiac rate and the peripheral resis-tance in the arterioles produced by the activity of sphincter muscles under control of the ANS. As in the case of heart rate, neutral hypnosis usually neither raises nor lowers blood pressure, but the relaxation effect may reduce the systolic pressure slightly, and any apprehensions that the subject has may raise it. On the other hand, suggestions can produce marked changes of up to 40 millimeters of mercury systolic pressure and 20 millimeters of mercury effect on the systolic pressure, and suggestions of temperature change primarily affect the diastolic pressure. Suggestions of warmth lower the diastolic pressure, and suggestions of cold raise it. Holroyd, Nuechterlein, and Shapiro 982) found that hypnosis reduced systolic blood pressure when bio-feedback did not, but biofeedback was superior to hypnosis in reducing forehead muscle tension. These effects were independent of subjects' hypnotic susceptibility.

A large number of clinical reports are cited by Crasilneck and Hall (1959) to the effect that bleeding can be increased or decreased by hypnotic sug-gestion, although they report a failure to demonstrate such a relationship experimentally. Some clinical sources describe reduction in bleeding as a concomitant of hypnoanesthesia even in the absence of specific suggestions to this effect. Arons believes that only capillary bleeding can be controlled hypnotically because veins have no sphincter muscles. A research difficulty results from the fact that venous, and certainly arterial, bleeding requires immeditate control, so anything less than immediate and total control over them produced by hypnosis is not likely to be experimentally measurable.