Expiratory Phase Of Respiration Research Articles

Clinical, physiological, and radiological different phenotypes of COPD patients

BackgroundCOPD is a heterogeneous lung disorder with multiple phenotypes and endotypes. This study aimed to identify the diverse clinical, physiological, and radiological phenotypes of COPD. Moreover, to provide whether there was a possible relation between FEV1%, FVC%, and FEV1/FVC ratio, [both before and after broncho-dilation with the diameters of the airway at three diverse levels throughout both inspiratory and expiratory phases of respiration].ResultsThis study included 50 cases, that were classified according to the radiological phenotypes into 5 groups [29 cases (58%) were mild [centrilobular emphysema) CLE)], 8 cases (16%) were moderate CLE, 5 cases (10%) were [confluent emphysema (CON)], 5 cases (10%) were [advanced destructive emphysema (ADE)] and 3 cases (6%) were [para septal emphysema (PSE)]. There was no considerable variance in the frequency of COPD clinical phenotypes among the diverse radiological phenotypes. There was a moderate positive correlation between the predicted FEV1% and the corresponding inter-luminal diameter at the selected levels (RB1, and LB3) in the inspiratory phase of respiration (P < 0.001 and p = 0.001 respectively) (r = 0.58, 0.46 respectively). and there was a moderate positive correlation in the expiratory phase of respiration between the predicted FEV1% and the equivalent inter-luminal diameter at the selected levels (RB1, and LB3) (P < 0.001 respectively) (r = 0.62, 0.51 respectively).ConclusionsWe confirmed that COPD is a highly heterogeneous illness, with multiple diverse clinical, physiological, and radiological phenotypes. Furthermore, HRCT can well be allied with pulmonary function tests (PFT).

OPPORTUNITIES OF LOW-DOSE DIGITAL FLUOROGRAPHY IN DIAGNOSIS OF PHENOTYPIC VARIANTS OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE

Objective. To determine the opportunities of low-dose digital fluorography (LDDF) in differential diagnosis of phenotypic variants of chronic obstructive pulmonary disease (COPD).Material and methods. There were 107 patients with clinically diagnosed COPD of varying severity examined. The average age of the patients was 51.8±1.5 years (46–59 years). All patients for LDDF of the chest in the frontal projection in the inspiratory and expiratory phase of respiration were undergone.Results. The electron optical density of the lungs was determined in the upper, middle and lower zones of both lungs. As a result in patients with a predominance of emphysematous variant of COPD (n=15) the most characteristic radiological symptom was lung hyperventilation (14% of 107 patients) and inspiratory electron optical density value was 748.18±4.72 optical density units (ODU). In patients with a predominance of bronchitic variant of COPD (n=43) the most common radiological symptom was the presence of symptom amplification and deformation of lung pattern (40% of 107 patients) and inspiratory electron optical density value was 668.04±12.26 ODU. For patients with mixed phenotypic variant of COPD (n=49) it was characterized by a combination of X-ray symptom amplification and deformation of lung pattern with lung emphysema (46% of 107 patients); the average value of inspiratory electron optical density value was 815.24±17.25 ODU.Conclusion. The technique of LDDF can detect X-ray symptoms and determine inspiratory and expiratory electron optical density of the lungs in patients with COPD that allows optimizing the differential diagnosis of phenotypic variants of chronic obstructive pulmonary disease.

Median arcuate ligament syndrome diagnosed on multi-detector computed tomographic angiography

Median arcuate ligament syndrome or coeliac artery compression syndrome is one of the abdominal vascular compression syndromes characterized by postprandial intestinal angina in the expiratory phase of respiration due to focal proximal coeliac root compression by a fibrous ligamentous band with resultant inadequate blood supply to the respectively supplied part of the gastrointestinal tract. Multi-detector computed tomography is extremely useful noninvasive modality in differentiating the cause of compression of the coeliac artery along with evaluation of collaterals due to multiplanar imaging capability.

B-mode ultrasonographic measurement of inferior vena cava diameter among healthy adults in Kano, Nigeria

Background: The inferior vena cava (IVC) is thin-walled compliant vessel that adjust the body volume status by changing its diameter depending on the total body fluid volume. sonographic measurement of IVC diameter has been reported as an alternative, rapid and non-invasive method of volume assessment of body fluids. The aim of this study is to determine the normal IVC diameter among healthy adults in Kano, Nigeria. Materials and Methods: Sonographic measurement of IVC of healthy adults with age ranging between 15 and 65 years was done with the subject in the supine position. The intrahepatic portion of its diameter was measured at about 2 cm proximal to the hepatic veins in a longitudinal plane in both inspiratory and expiratory phases of respiration. Three repeated measurements were done to reduce intra-observer variability in this prospective cross-sectional study. Results: A total of 400 adults comprising 173 (43.3%) males and 227 (56.8%) females were recruited using Fisher's statistical formula for sample size determination. The mean age of the subjects was 32.4 ± standard deviation 10.9 years. The mean inspiratory diameter was 10.1 ± 2.7 mm (ranging from 4.8 mm to 18.8 mm). The overall mean IVC expiratory (IVCexp) diameter in this study was 16.7 ± 2.7 mm (range = 10.9–25.4 mm). The mean IVCexp diameter was slightly higher for males than for females (males: 17.1 ± 2.8 mm; females: 16.3 ± 2.7 mm). This difference was statistically significant ( P = 0.0022). There was a gradual decrease in IVC diameter with advancing age. Conclusion: This study was able to generate normal IVC diameter in a sample of Nigerians which may serve as a reference for normal values in Black Africans.

Use of Nasal Continuous Positive Airway Pressure as a Mode of Respiratory Support in Newborns at SAT Hospital, Trivandrum

Background: Respiratory distress is one of the leading causes of mortality in a newborn ICU. Though endotracheal intubation and mechanical ventilation is the gold standard in the management of acute respiratory failure, it is not without complications. The Continuous positive airway pressure (CPAP) is used as an alternative for maintaining an increased trans-pulmonary pressure during expiratory phase of respiration in a spontaneously breathing infant. However CPAP is considered as effective as to mechanical ventilation and has fewer complications, its usefulness in a tertiary care ICU in resource poor settings is yet to be studied. Objective: To study the use of Nasal CPAP in managing respiratory distress in a tertiary care pediatric ICU. Methods: this descriptive study was performed in the 75 consecutive newborn babies with respiratory distress admitted in inborn nursery of SAT Hospital, Trivandrum. The Outcome measures are the efficacy of nasal CPAP as measured by improvement in Downe score as assessed at intervals after intervention. Results: A total of 75 infants were treated with nasal CPAP; of these, 55 infants (73.3%) improved with CPAP alone, 44 cases had Hyaline membrane disease out of these 63.63% improved with nasal CPAP, 13 (17.3%) died and 7 (9.3%) required ventilation. All cases with meconeum aspiration improved with nasal CPAP. There were no major complications like pneumothorax. Conclusions: Nasal CPAP seems to be a safe alternative to routine intubation and mechanical ventilation in managing respiratory distress cases in resource limited settings.

Breathing and swallowing in normal man - effects of changes in body position, bolus types, and respiratory drive

Coordination of breathing and swallowing is essential for airway protection and dyscoordination may cause morbidity and mortality. Using a recently developed technique for high accuracy respiratory measurements of airflow during swallowing, we investigated the effects of body position (upright vs left lateral), bolus type (spontaneously swallowed saliva vs water), and respiratory drive (normo- vs hypercapnia) on coordination of breathing and swallowing in 32 healthy volunteers. Swallows were in all cases (100%) proceded by expiration and 98% were also followed by expiration, regardless of body position, bolus type, or respiratory drive. While the endpoint of postswallow apnea correlated well to the endpoint of pharyngeal swallowing, duration of preswallow apnea was highly variable. In a small fraction of swallows followed by inspiration (3%), the expiratory phase before swallowing and duration of postswallow apnea was significantly longer. Body position and respiratory drive affected the increase in upper esophageal sphincter tone during inspiration. Increased respiratory drive also reduced swallowing frequency and shortened duration of preswallow apnea. Water swallows had longer duration of preswallow apnea. Swallowing occurs during the expiratory phase of respiration, and the fraction of swallows preceded and followed by expiration approach 100% in healthy humans. This integration between breathing and swallowing remains unchanged regardless of body position, bolus characteristics, or respiratory drive. Our results provide a platform for future studies aiming at understanding how this integration is changed by aging, diseases, and drugs.

Optical analysis of circuitry for respiratory rhythm in isolated brainstem of foetal mice

Respiratory rhythms arise from neurons situated in the ventral medulla. We are investigating their spatial and functional relationships optically by measuring changes in intracellular calcium using the fluorescent, calcium-sensitive dye Oregon Green 488 BAPTA-1 AM while simultaneously recording the regular firing of motoneurons in the phrenic nerve in isolated brainstem/spinal cord preparations of E17 to E19 mice. Responses of identified cells are associated breath by breath with inspiratory and expiratory phases of respiration and depend on CO(2) and pH levels. Optical methods including two-photon microscopy are being developed together with computational analyses. Analysis of the spatial pattern of neuronal activity associated with respiratory rhythm, including cross-correlation analysis, reveals a network distributed in the ventral medulla with intermingling of neurons that are active during separate phases of the rhythm. Our experiments, aimed at testing whether initiation of the respiratory rhythm depends on pacemaker neurons, on networks or a combination of both, suggest an important role for networks.

Novel motor gestures for phonation during inspiration enhance the acoustic complexity of birdsong.

Sound generation based on a pulmonary mechanism typically occurs during the expiratory phase of respiration. Phonation during inspiration has been postulated for the calls of some amphibians and for exceptional sounds in some human languages. No direct evidence exists for phonation during inspiration in birds, but such a mechanism has been proposed to explain very long uninterrupted songs. Here, we report the first physiological evidence for inspiratory sound production in the song of the zebra finch (Taeniopygia guttata). Motor gestures of the vocal and respiratory muscles leading to the production of inspiratory phonation differ from those of silent inspirations during song as well as from those leading to phonation during expiration. Inspiratory syllables have a high fundamental frequency, which makes them acoustically distinct from all other zebra finch song syllables. Furthermore, young zebra finches copy these inspiratory syllables from their tutor song, producing them during inspiration. This suggests that physical limitations confine the production of these sounds to the inspiratory phase in zebra finches. These findings directly demonstrate how novel respiratory-vocal coordination can enhance the acoustic structure of birdsong, and thus provide insight into the evolution of song complexity.

Differential effects of hypercapnia on expiratory phases of respiration in the piglet

Hypercapnia induces prolongation of expiratory time (T e) during early development. In the present study, we determined the response to steady state hypercapnia of three neural phases of the total respiratory cycle, inspiration (T i), stage 1 or passive expiration, T e-1 and stage 2 or active expiration, T e-2. Experiments were performed in decerebrate, vagotomized, spontaneously breathing piglets aged 5–10 days. Neural phases of the respiratory cycle were based on electrical activities of the thyroarytenoid (TA, laryngeal adductor) and triangularis sternii (TS, chest wall expiratory muscle) in relation to diaphragm (D) activity. We observed that hypercapnia induced prolongation of both expiratory phases. The greater prolongation of T e-1 was associated with an increase in TA activity and an increase in laryngeal resistance, which peaked early in T e-1, and then progressively decreased. These findings demonstrate that, in early postnatal life, a hypercapnia induced increase in respiratory drive is associated with centrally mediated prolongation of both phases of expiration, a greater prolongation of T e-1, and an increase in laryngeal resistance during post-inspiration. We speculate that the latter serves to optimize gas exchange by reducing large fluctuations in functional residual capacity.

Respiratory responses to unsupported arm lifts paced during expiration.

Unsupported arm exercise endurance is reduced in both normal subjects and patients with chronic obstructive pulmonary disease in association with an increase in dyspnea and alterations in the pattern of respiratory muscle recruitment. Some report greater difficulty carrying out arm activity paced during the expiratory phase of respiration rather than during inspiration. The purpose of this study was to determine the effect of unsupported arm exercise lifts paced in phase with expiration (EUAL) on (a) diaphragm recruitment measured as the electromyographic amplitude (EMG-DI), (b) the pattern of thoracoabdominal motion measured with inductive plethysmography, and (c) the sensation of dyspnea measured with a 100 mm visual analog scale. Data were collected from 18 normal adult subjects at baseline and during EUAL. When compared with rest, EUAL resulted in significant increases in mean inspiratory and expiratory diaphragm EMG amplitudes, dyssynchronous thoracoabdominal motion, and dyspnea intensity. These changes in diaphragm recruitment and thoracoabdominal motion may in part explain reports of increased dyspnea intensity with unsupported arm exercise.

Some reflex cardioinhibitory responses in the cat and their modulation by central inspiratory neuronal activity.

1. Cats were anaesthetized with a mixture of chloralose and urethane, and were artifically ventilated. 2. An open pneumothorax was provided by two large-bore tubes which were sealed in the sixth intercostal space on each side. They were connected to a Fleisch pneumotachograph. Phasic changes in central inspiratory neuronal activity were measured quantitatively as changes in the volume of the pneumothorax during temporary interruption of artificial respiration, the volume of the lungs being held constant at their end-expiratory level. In this way the activity of slowly adapting pulmonary stretch receptors was maintained constant. 3. Reflex cardioinhibitory responses were elicited by stimulation of (a) the carotid body chemoreceptors by intracarotid injections of cyanide; (b) the arterial baroreflex by controlled elevations of the blood pressure; (c) cardiac receptors by left atrial injections of veratridine; and (d) pulmonary C fibres (including J receptors) by right atrial injections of phenylbiguanide. 4. The effects of central inspiratory neuronal activity on pulse interval were assessed by comparing the values observed during the inspiratory and expiratory phases of the respiratory cycle in the control state and during stimulation of each cardiovascular receptor group. 5. The carotid chemoreceptor-induced bradycardia measured during the expiratory phase of respiration was reduced during inspiration to a value of about 15% of control. The central inspiratory drive was less effective in altering the reflex responses from the arterial baroreceptors and cardiac receptors, the corresponding values being 42 and 51% respectively. 6. In contrast, the bradycardia evoked by pulmonary C fibre stimulation was not significantly affected by the central inspiratory drive. 7. The differential nature of the modulation by the central inspiratory drive occurred independently of the integrity of the sympathetic nerve supply to the heart indicating that the cardiac efferents involved were largely fibres in the vagus nerves. 8. The possible explanation of these results in terms of central mechanisms is discussed.

Contributions of syringeal muscles to respiration and vocalization in the zebra finch

Acute and chronic electromyographic (EMG) recordings from individual syringeal muscles were used to study syringeal participation in respiration and vocalization. In anesthetized birds, all syringeal muscles recorded were active to some degree during the expiratory phase of respiration, following activity in the abdominal musculature and preceding the emergence of breath from the nostril. In awake birds, the ventralis (V) muscle fired a strong, consistent burst, but the dorsalis (D) was variable both in strength and timing. Denervation of V is sufficient to produce the wheezing respiration originally seen in birds with complete bilateral section of the tracheosyringeal nerve. Complete syringeal denervation also removed almost all the acoustic features that distinguish individual song syllables, but had a minor effect on the temporal structure of song. When activity in V and D was recorded in awake, vocalizing birds, D was active before and during sound production, and V showed a small burst before sound onset and a vigorous burst timed to the termination of sound. During song, V was consistently active at sound offset, but also participated during sound for narrow bandwidth syllables. For some syllables (simple harmonic stacks), neither muscle was active. These data suggest that V contributes to syllable termination during vocalization and may silence the syrinx during normal respiration. D contributes to the acoustic structure of most syllables, and V may contribute to a special subset of syllables. In summary, the syringeal muscles show different activity patterns during respiration and vocalization and can be independently activated during vocalization, depending on the syllable produced.

Weak Sensory Stimuli Induce a Phase Sensitive Bradycardia

We attempted to demonstrate that significant perceptual stimuli would induce different degrees of heart rate deceleration depending on when (phase) in the cardiac cycle they occurred. Relative to previous work, we concurrently examined a number of factors that might alter the amplitude of such a cardiac cycle time effect. Stimulus intensity and presence or absence of a speeded response were manipulated. Liminal stimuli and a perceptual rather than motor set were expected to maximize any cardiac cycle time effect. Respiratory phase, length of average interbeat interval, and number of trials were also investigated. Twenty-four college aged, male volunteers were randomly separated into equal groups receiving instructions either to judge which of two weak visual stimuli occurred or to execute a speeded, discriminative response to the stimuli. Discriminative stimuli were presented at either 0, 150, 250, 350, or 500 ms after the R-wave of the electrocardiogram. Stimuli were presented with an intensity that had yielded either 63% or 90% correct detections in a prior psychophysical assessment. A phase dependent deceleration occurred after both intensities of stimuli. Poststimulus deceleration was greater for stimuli in early to mid cycle as suggested by earlier work. As expected, this result was clear when the stimuli were presented during the expiratory phase of respiration. Neither perceptual/motor set nor stimulus intensity altered the phase sensitive deceleration. Thus, phase sensitive deceleration was confirmed using demanding sensory stimuli and an improved representational technique.

The Evaluation of Laryngeal Changes Occurring During Exercise and Exercise-Induced Asthma

Dr Charles Hurbis won first prize in the resident essay contest at the annual meeting of the American Broncho Esophagological Association, Palm Beach, Fla, for his study of exercise-related laryngeal changes in 15 normal subjects and 15 subjects with exercise-induced asthma. Flexible laryngoscopy was performed at rest and during exercise on all 30 subjects. No exercise-related changes occurred during the inspiratory phase of respiration with exercise in any of the subjects. Significant group-specific changes in the size of the glottic airway were seen during the expiratory phase of respiration with exercise. Normal patients increased their glottic area during expiration. Patients with mild to moderate exercise-induced asthma

Pharmacologic Management of Childhood Asthma

Asthma is characterized by an increased responsiveness of the airways to various stimuli, which results in narrowing of the airways and in a prolongation of the expiratory phase of respiration; in the early phase the airway obstruction is usually completely reversible, either spontaneously or as a result of therapy. There are three therapeutic approaches to asthma: the avoidance of allergens and irritants causing or aggravating the disease; the use of immunotherapy; and the use of pharmacologic agents. Increasing knowledge of the pathophysiologic aspects of bronchial asthma in the past decade has led to significant advances in its pharmacologic management. The basic alteration of respiratory function is an increased resistance to flow of air through the airway secondary to a combination of three factors: smooth muscle spasm, mucosal edema, and retained viscid secretions. In mild asthma and during remissions the airways less than 2 mm in diameter (the small airways) are obstructed, whereas during an acute attack and with chronicity, both small and large airways are involved. Although both phases of respirations are affected, the increased airway obstruction is more pronounced during expiration. EVALUATION OF THE ASTHMATIC CHILD The diagnosis of asthma is based on history, characteristic physical findings and laboratory tests. Asthmatic attacks of infants are usually associated with viral upper respiratory infections; the infants are usually febrile and frequently have otitis media.

Respiratory modulation of barareceptor and chemoreceptor reflexes affecting heart rate and cardiac vagal efferent nerve activity.

1. Brief stimuli were delivered to the carotid chemoreceptors or baroreceptors in dogs anaesthetized with chloralose. Chemoreceptor stimulation was achieved by rapid retrograde injection of 0.2-0.5 ml. CO2 equilibrated saline through a cannula in the external carotid artery. Baroreceptor stimulation was achieved by forceful retrograde injection of 2-5 ml. air-equilibrated saline into the external carotid artery after first clamping the common carotid artery. 2. prompt decreases in heart rate were elicited by brief sudden chemoreceptor or baroreceptor stimuli when these were delivered during the expiratory phase of respiration. The stimuli did not modify the control heart rate pattern when delivered in the inspiratory phase of respiration. This respiratory modulation of reflex effectiveness persisted when the animals were completely paralysed and the phase of the respiratory cycle was monitored through a phrenic electroneurogram. 3. single cardiac vagal efferent nerve fibres were dissected from the cut central end of the right cervical vagus nerve. They were classified as cardiac efferents by their cardiac and respiratory rhythmicity, and by their increased activity in response to stimulation of a carotid sinus nerve or to mechanical elevation of the systemic arterial pressure. These efferent fibres increased their activity in response to brief chemoreceptor or baroreceptor stimuli delivered in expiration, but did not respond to stimuli delivered in inspiration. This respiratory modulation of both reflexes persisted after bilateral cervical vagotomy.

Effects of temperature and wind on facial temperature, heart rate, and sensation.

Skin temperature measurements of the face have shown that the cheek cools faster than the nose and the nose faster than the forehead. The cooling effect of wind is maximum at wind speeds between 4.5 and 6.7 m/s. Cold winds produce significant bradycardia, which is, however, much more pronounced during the expiratory phase of respiration. A significant correlation was noted between cooling of face and the reflex bradycardia observed. Similarly, a very significant correlation was noted between drop in skin temperature and subjective evaluation of cold discomfort. Consequently, the drop in skin temperature, reflex bradycardia, and subjective evaluation are parameters which are directly affected by cold wind and can be used as adequate indicators of the degree of discomfort. When comparing the present results with the windchill index, it was found that in the zone described as "dangerously cold" the index fits well with the physiological measurements. In the zone described as "bitterly cold," the index by comparison with actual skin temperature measurements and subjective evaluation underestimates the cooling effects of combined temperature and wind by approximately 10 degrees C.

Baroreceptor and chemoreceptor influences on heart rate during the respiratory cycle in the dog.

1. Brief stimuli were delivered to the carotid chemoreceptors or baroreceptors in dogs anaesthetized with pentobarbitone or chloralose. Chemoreceptor stimulation was achieved by rapid retrograde injections of 0-2-0-5 ml. warmed, CO2-equilibrated saline through a cannula in the external carotid artery. Baroreceptor stimulation was achieved by forceful retrograde injection of 2-5 ml. air-equilibrated saline, or of freshly drawn arterial blood, into the external carotid artery after first clamping the common carotid artery. 2. Brief baroreceptor stimuli had no noticeable effect on breathing. Brief chemoreceptor stimuli had no effect on breathing in some dogs, but in many produced a reflex increase in the depth of inspiration when delivered during inspiration. In these same dogs, brief chemoreceptor stimuli delivered in expiration either prolonged the expiratory pause or evoked an active expiratory effort. 3. Prompt decreases in heart rate were elicited by brief sudden chemoreceptor or baroreceptor stimuli when these were delivered during the expiratory phase of respiration. The stimuli did not modify the control heart rate pattern when delivered during inspiration. If the carotid sinus nerve or the vagus nerves were cut the responses were abolished. 4. Brief chemoreceptor or baroreceptor stimuli remained effective in evoking prompt decreases in heart rate during periods of apnoea in the end-inspiratory position (Hering-Breuer inflation reflex). In periods of apnoea after prolonged artificial hyperventilation the stimuli were sometimes ineffective at first, but were always effective late in the period of apnoea, again producing prompt cardiac slowing. 5. After denervation of the lungs, brief baroreceptor and chemoreceptor stimuli continued to evoke prompt falls in heart rate when given during expiration. When delivered during inspiration the same stimuli were either ineffective, or less effective.

"STRETCHING" OF THE ARTERIES IN RENAL ARTERIOGRAPHY.

Commonly the left, and sometimes both, renal arteries are found on renal arteriograms to be tortuous. In this event, the overlapping shadows prevent proper evaluation of the vessels. Overlapping of the renal artery shadows is ordinarily of no significance when arteriography has been performed for intra-renal masses. It is, however, of considerable importance in suspected renal artery occlusive disease, especially fibromuscular hyperplasia (1, 2, 4). Here, not only can the tortuosity conceal minor and even severe areas of fibromuscular hyperplasia, but prominent tortuosity may simulate the appearance of the condition where it does not exist. At the University of California Medical Center, San Francisco, renal arteriography is performed whenever possible by the Seldinger technic (3), with the patient supine. In the past, whenever tortuous renal arteries overlapped on the standard supine arteriogram obtained in the neutral or expiratory phase of respiration, the study was repeated with the patient upright. T...

An active expiratory muscle in the chicken which is inhibited by stimulation of the central end of the vagus. A demonstration

In mammals expiration is passive under ordinary conditions. It is only under abnormal conditions that certain muscles become active during the expiratory phase of respiration. At the last meeting of the Federation of American Societies for Experimental Biology we made the statement that in the fowl normal expiration is active. We wish to demonstrate the truth of this statement by a graphic method. We have found that the innermost of the abdominal muscles in the chicken when carefully isolated contracts regularly with each expiration. When the contractions of this muscle are recorded simultaneously with the movements of the thorax it will be observed that the muscle contracts during expiration and suddenly relaxes during the onset of inspiration. The literature concerning the effect upon the respiration of stimulation of the central end of the vagus in mammals is very extensive and full of conflicting opinion as to the nature of this effect. In fowls stimulation of the central end of the vagus causes an unmistakable inhibition of the contractions of this muscle. When the movements of the thorax and the contractions of the expiratory muscle are registered simultaneously, stimulation of the central end of the vagus brings out an instructive picture. Throughout the period of stimulation the thorax remains quiescent in an inspiratory position, while the expiratory muscle remains completely relaxed. This phenomenon is another instance of the general law of “ contrary innervation ” (Meltzer), or I “reciprocal innervation” (Sherrington). Inhibition of the expiratory group of muscles during inspiration was suggested by one of us over thirty years ago.