Blood-pressure in medicine and surgery; a guide for students and practitioners

Preface

In the opinion of so eminent a physiologist as Ludwig, the discovery of blood-pressure by Stephen Hales was more important than that of the circulation of the blood by Harvey. As far as its clinical application was concerned, the study of blood-pressure languished for many years, owing to the difficulty which attended its estimation in man. With the description by Riva-Rocci, in 1899, of an instrument which, by its very simplicity, immediately won universal recognition, the importance of sphygmomanometry began to be appreciated.

The clinical study of blood-pressure is but a decade old, but in these few years it has furnished a great amount of diagnostic, prognostic, and therapeutic information. Some there are who still cling to the belief that the finger is just as trustworthy in estimating the arterial pressure as is the sphygmomanometer, but to those who have given the subject more careful consideration this contention seems extravagant. The sense of touch is, in some, more highly developed than in others; yet the man who seriously states that he is able to measure bodily temperature by palpation alone, is no more in error than is he who presumes to gauge the blood-pressure by means of the finger. An argument for the truth of this statement may be afforded to anyone who will palpate the radial artery and " guess," for it is only a conjecture, the degree of blood-pressure before using

Vl PREFACE

the sphygmomanometer. The marked discrepancies between the results furnished by the two procedures, even after many years in practice, will be proof enough of the value of the instrument. The sphygmomanometer is now as much a part of the physician's proper armamentarium as are the clinical thermometer and the stethoscope, and the assistance which may be expected from its routine employment should also be as familiar to him.

It has been the author's aim to make fully available the assistance which the study of blood-pressure affords in the diagnosis, prognosis, and treatment of disease. The essentials are covered, and if after mastering them the reader is so disposed, he may range at will in an almost inexhaustible literature. E. H. G.

Philadelphia, 1914.

Chapter I. Physiology Of Blood-pressure

It is essential, in studying blood-pressure, that one should be informed concerning its physiology, for without knowledge of the physiological mechanism which plays such an important role, an intelligent comprehension of the sphygmomanometer is impossible. The human blood-pressure system comprises essentially, (1) the heart; (2) the bloodvessels; and (3) the vasomotor regulating mechanism. The three are so intimately associated that disturbance of any one is followed by a derangement of the balance existing among the three.

I. MAINTENANCE OF BLOOD-PRESSURE.

Heart and Bloodvessels. — As far as the heart and bloodvessels are concerned, blood-pressure depends essentially on three factors: (a) the energy of the heart; (b) the peripheral resistance, and (c) the volume of the blood. The first two are of great importance, while the last has but a theoretical interest.

II. BLOOD-FLOW IN ARTERIES.

The vascular tree consists of a finely divided system of elastic tubes, the blood flowing through the arteries, through the capillaries, to the veins, the pressure being highest in 2 the arteries and lowest in the veins. This is designed for the movement of the column of blood, as a fluid must flow from the point of highest pressure to the point of lowest pressure. It is through the* activity of the heart that the difference in pressure is maintained. When, for any reason, the heart ceases to functionate, the circulation continues, that is, the blood flows, despite the failure of the heart, from artery to vein, until the pressure in these two branches of the vascular system has become equalized, at which moment the blood stream comes to a standstill.

Despite the periodic activity of the heart, the blood is sent through the vessels in a continuous current, the reasons being, (1) the resistance offered by the arterioles and capillaries, and (2) the elasticity of the arterial wall. These two physicial properties of the vessels prevent stagnation of the blood during diastole, and account for its propulsion during this phase of the cardiac cycle. The elastic property of the arteries is especially concerned, for the vessel beingput on the stretch during systole, stores up this energy to discharge it during diastole, thereby contracting the artery and expelling the blood. One might almost speak of this as an echo of the cardiac systole arising in the arteries.

Langendorff's modification of Weber's scheme of the circulation, conveys a good idea of the general physical features of the latter.

H is a rubber bag corresponding to the heart, V and V" represent the inlet and outlet valves of the heart. The rubber tubing A is the arterial and V the venous system, each being provided with a pressure gauge, M" and M' respectively. C is a sponge in a glass tube which represents the resistance offered by the capillaries, the whole apparatus being filled with water. If one presses rhythmically on the bulb H, the valves V and V" act as in vivo, the column of water rises in M " and sinks in M f , while the tube A becomes more tense and the tube V more relaxed. As a result of the cardiac activity ( H) the pressure in the arteries is higher than in the veins, owing to the resistance in C. In the diastolic pause (release of pressure on the bulb) the pressure in A falls, and that in V rises, and the water is sent forward

BLOOD-FLOW IN CAPILLARIES AND VEINS despite the cessation of the activity of H. If particles are suspended in the water, the movement of the fluid can be plainly seen.

Fig. 1

W

Weber's scheme of the circulation.

When compression on H is discontinued, the circulation persists until the column of fluid in M" stands at the same level as that in M' '. This experiment serves to confirm the statement that the principal driving force for the arterial circulation is to be found in the heart and elasticity of the vessel walls. In addition to this force may be mentioned the contractile power of the arteries inherent in the smooth muscle fibers of the media.

III. BLOOD-FLOW IN CAPILLARIES AND VEINS.

By the time the blood arrives at the smaller arteries, little is to be seen of the rhythmic activity of the heart, that is, pulsation is generally no longer appreciated, and when the capillaries are reached, there is no pulsation at all (excepting in pathological states), although they do possess the power of contraction. By the time the blood gets to the veins, the force of the cardiac systole is nil, and for the propulsion through this part of the vascular tree, the negative pressure in the thorax and the aspiration of blood by the diastole of the heart are called into play.

Newer researches have demonstrated that certain veins are supplied with constrictor fibers, such as the portal vein, which receives branches from the splanchnic nerves, and it has been suggested, and indeed almost proved, that the systemic veins have a vasomotor control. Just how much influence these vasomotor nerves have in the circulation of blood in the veins is uncertain.

IV. BLOOD-PRESSURE.

1. Resistance of Bloodvessels. — In a system of tubes, such as is represented by the vascular apparatus, the blood exerts equal pressure on all parts of the vessel wall at a given point, but the pressure varies proportionately with the amount of resistance the blood has to overcome.

Were the circulatory apparatus a rigid, unyielding set of tubes, the pressure would diminish in direct proportion to the distance from the heart. We have said above, that the pressure in a system of tubes depends largely on the amount of resistance which the circulating fluid has to overcome. This resistance does not arise from contact of the fluid with the vessel wall, for the fluid in direct contact with the latter is at rest, and therefore the friction must take place within the blood itself, the degree depending on the viscosity of the fluid. The amount of resistance which a constant uniform viscosity exerts is dependent on the length and diameter of the tube or vessel, and follows the law of Poiseuille. According to the latter:

Q =k-n

Q equals the amount of fluid per second issuing from a tube, d equals the diameter, / equals the length of tube, and h equals the amount of pressure necessary to drive blood through the vessel; k is the constant of internal friction. Hurthle has shown that this formula holds good for blood as well as for homogeneous fluids, but he claims the law is not applicable to a finely divided system of tubes like the arterial tree, on account of the elastic properties of the vessel wall. He prefers to regard the flow of blood, with decreasing blood-pressure as slower than would be deduced from Poiseuille's law. 1

2. Pressure in the Various Parts of the Cardiovascular System. — There is but little difference in pressure in the larger divisions of the arterial tree, and it is not until the finest arterioles and capillaries are reached that a material decrease is observed. This decrease is still more noticeable in the veins and is lowest where the vense cavse empty into the heart. Some observers have claimed that pressure in the iliacs is higher than in the carotids, but Weber 2 using improved methods, demonstrates that this is impossible, and never occurs in health.

The pressure in the veins is variable, as the following table of Jakobson (Langendorff) will show:

Mm. Hg.

V. cruralis 11.4

V. brachialis 4.1

V. facial, anterior 3.0

V. jugularis 0.2

V. anonym'a 0.1

(From estimations made on sheep.)

Findlay 3 has studied in the child and in the adult, the difference between central systolic pressure and peripheral pressure, using the Riva-Rocci instrument for the former and the Gartner tonometer for the latter. During childhood, the systolic pressure is uniform at different points of the circulation, but in adult life, the peripheral is lower than the central, this difference in pressure increasing with age. In cases of hypertension, the greater the pressure, the greater

1 Berlin, klin. Woch., 1912, p. 773.

the difference between central and peripheral pressures.

Concerning the force which is necessary to rupture the normal artery, Grehaut and Quinquaud 1 found that the pressure in the carotid being equal to 150 mm. of mercury, 7 to 11 atmospheres are required to rupture the vessel, or from 35 to 56 times more pressure than normally exists. As a general rule, it may be stated that arteries of smaller calibre are more resistant than arteries of larger calibre, the aorta, for instance, being ruptured by less pressure than the radial. This rule holds especially in pathological states. The pressure exerted on the human artery at the moment of rupture varies from 13 to 25 kilograms. The veins are but a little less resistant than the arteries. In pathologic states, as cerebral hemorrhage, the right carotid could be broken at 3.3 atmospheres and the left at 3.4 atmospheres. The arteries near the lesion are still less resistant, the sylvian artery breaking at 3 atmospheres.

3. Maintenance of Blood-pressure. — (a) Energy of the Heart. — This is a very important factor in the maintenance of blood-pressure, and plays a prominent role in its variations. All of the five inherent properties of the cardiac muscle share in this, rhythmicity, excitability, contractility, conductivity, and tonicity. Moreover, the amount of blood leaving the heart in a specified time has a relatively important share in the changes seen in blood-pressure. In general, it may be stated that increase in heart rate raises the blood-pressure, and that a lowered rate diminishes pressure. This is w^ell illustrated by a tracing taken from Langendorff showing the effect on blood-pressure of a slow heart rate brought about by the stimulation of the vagus.

Note. — Experiments after cutting both vagi show that with the increased pulse rate there is an increase of blood-pressure.

There are, however, many clinical observations which do not corroborate this otherwise very simply postulate, as high blood-pressure is sometimes associated with a relatively slow heart. This is scarcely a contradiction to the general statement that increase in heart rate raises blood-pressure,

1 Journal de l'Anat. et de Physiol., 1885, xxi, p. 287.

since we have a corollary to it in the axiom that blood-pressure depends, in addition to the heart rate, upon the amount of blood leaving the heart in a unit of time. It is readily comprehensible that a slow heart by means of its long systole can discharge a quantity of blood sufficient to counteract its pressure-lowering effects. On the other hand, it is equally true, clinically, that a rapid heart is frequently associated with low blood-pressure, as on account of the cardiac rate, there is insufficient filling of the ventricle with blood, this serving to offset the blood-raising tendencies f the rapid heart.

Fig. 2

\AV N v^

Decrease in heart rate and fall in blood-pressure. Stimulation of vagi.

Another purely cardiac factor in blood-pressure is the strength of the cardiac systole, which, when powerful, always raises the blood-pressure. This increased force of the heart systole is generally associated with increased resistance in the peripheral circulation, or, to express it in another way, the increased force of the heart is generally a consequence of increased resistance, and not due entirely to changes in the inotropic nerve mechanism.

(b) Peripheral Resistance. — It is apparent that without resistance there can be no pressure, and it is equally apparent that the following law is applicable: the greater the resistance, the higher the pressure, other things being equal. Increased viscosity of the blood has been held to be one of the causes of increased resistance, and some observers have described a polycythemia hypertonica, the hypertension being due to the increase in the number of red blood cells. This is discussed at length in the chapter on heart and blood conditions, under the heading polycythemia. The internal friction of the blood may have a great influence in raising blood-pressure but very little evidence has been adduced as proof. The success of potassium iodide in cases of hypertension has been ascribed to its ability to diminish the viscosity, and thus lessen the high blood-pressure.

Of far greater importance is the change in the size of the bloodvessels, whereby their lumen is increased or decreased, thus diminishing or increasing the resistance respectively. The arteries are provided with a musculature absolutely under the control of the nervous mechanism which regulates the dilatation and constriction of the vessels. This vasomotor tone will be considered in more detail on page 25, but it may be said that its normal balance is most important for the preservation of good health. If the vasomotor tone is weakened through any cause, there is a great fall in pressure owing to the evident general arterial dilatation. Great depression of blood-pressure follows, due to congestion of the vessels in the splanchnic field, which, we shall learn later, is able to accommodate all the blood of the body.

Local, not extended, vascular dilatation is without effect on the systemic blood-pressure, although the reverse cannot be so positively stated.

(c) Volume of the Blood. — This plays a subordinate role, in the maintenance of blood-pressure. The volume of the circulating fluid can be much increased, without any appreciable effect on blood-pressure, provided the increase takes place slowly. This is seen experimentally by the injection of physiological salt solution and other substances into animals. Failure, thus to raise blood-pressure, is due to three factors: (1) the rapid interchange between the vessels and tissues; (2) the automatical dilatation of the bloodvessels in order to adjust themselves to the increased amount of fluid, and (3) the subsequent polyuria. The last is the most important, the amount of urine running pari passu with the amount injected.

On the other hand, losses of blood do decrease, if but temporarily, the blood-pressure, so that one must, in a dog, at least, remove about one-fifth of the total quantity of blood before any great depression of blood-pressure is seen. In man, the loss of one-half of the amount of blood causes death (3-3.5 per cent, of body w T eight).

4. Vasomotor Regulating Mechanism. — (a) Vasomotor Nerves. — The smooth muscle of the arteries was discovered by Henle, and soon thereafter Stilling and Henle hinted at the presence of vasomotor nerves whose existence was later proved by Claude Bernard, in 1852. To SchifT, Ludwig, and Thiry we are indebted for the proof of the vasomotor centre.

When a nerve which controls the vessels is cut, there will be a suffusion of the area supplied by the vessels under the control of this nerve, also an increase of the warmth and size of the part and of the blood pouring from the veins. Stimulation of the same nerve has the opposite effect. Depending on the extent of the vessel's nerve distribution, there will be a fall or rise in systemic arterial blood-pressure, following severing or stimulation of the nerve respectively.

The vasomotor nerves are distributed in the musculature of the media, and since the muscle fibers are circular in their arrangement, the effect of stimulation is to constrict the lumen of the vessel (vasoconstrictor nerves). The vasodilator nerves are but little understood. Dilatation of the vessels has been held to be due to the influence of the longitudinal muscle fibers acting in opposition to the circular musculature, but Goltz believes that vascular dilatation is due to inhibitory nerves, which oppose the vasoconstrictor fibers. It is supposed by recent investigators that both varieties of nerve fibers are present in the same nerve trunk, and that depending on the quality of the irritant constriction or dilatation is effected. This view has been held by Pal, Strieker, and others to explain the occurrence at one time of vasoconstriction and at another time of vasodilatation, as for instance, in the crises of tabes dorsalis.

(b) Vasomotor Centre. — That there is a vasomotor regulating centre has long since been definitely proved. When the spinal cord in the region of the cervical portion is severed from the medulla, the blood-pressure falls, and when the same region is stimulated there will be a rise in pressure, both phenomena being brought about by dilatation and constriction respectively, of the vessels in the splanchnic field. The seat of this vasomotor centre is in the upper part of the medulla. The centre is automatic in its activity. It is influenced principally by three factors: (1) psychic states, (2) gaseous composition of the blood, and (3) reflexly, by cutaneous influences.

(1) Psychic Influences. — The result of psychic influences is seen in pallor from fear, and in flushing, as a result of shame or anger, although it cannot be denied that there is an associated cardiac participation in these phenomena.

(2) Gaseous Composition of the Blood. — Whenever there is dyspnea the blood-pressure rises through stimulation of the vasomotor centre, some believe, from the diminished amount of oxygen and others from the increased amount of carbon dioxid. If the breath is held, the same phenomenon is observed. Fig. 3 shows the effect on blood-pressure of artificial respiration in a curarized animal (x).

When both vagi are cut, a curious phenomenon is observed, one which has been the ground for much dispute in physiological circles. Certain waves appear while the arterial blood-pressure is being registered (Fig. 4), consisting of undulations which show an ascending tendency (Traube-Hering waves). The waves are synchronous with respiration, and are intimately associated with the respiratory and vasomotor centres. Cushing 1 observed them when the vasomotor

1 Amer. Jour. Med. Sci., 1902, exxiv, p. 392.

centre was evidently trying to overcome whatever was producing the bulbar anemia. On comparing the waves with the intracranial tension he was able to establish the fact that the crests of the waves rose above and the hollows

Fig. 3

[ Effect on blood-pressure of artificial respiration in a curarized animal.

fell below the intracranial pressure, and, furthermore, that the rise and fall of the waves was associated with blanching and reddening of the cortex. Cushing believes that the phenomenon is but an exaggeration of the normal rhythmic waves of blood-pressure seen under many conditions.

Fig. 4

Traube-Hering waves.

Wolf and Plumier 1 regard the Traube-Hering waves as an expression of rhythmical vasoconstriction extending to all the vessels of the body, arising from a stimulus sent out

1 Journal de Physiol, et de Path, gen., 1904, p. 213.

from the respiratory centre to the vasomotor centre at each inspiration. The heart plays little part in the production of these waves.

Rhythmical variations of true cardiac origin have been described by Cushing. 1 Knoll, 2 Winterberg, 3 and Straschesko. 4

For a full discussion on the recognition of the various waves of blood-pressure, the reader is referred to an able article by Morawitz. 5

(3) Reflex Influences. — Very mild irritants applied to the skin, such as blowing on the skin, or light contact, cause a rise in pressure but strong stimuli are without effect. Certain sensory nerves, which, when stimulated, give rise to increase of blood-pressure, have a depressor function when the stimulus is applied to narcosis. Such a nerve possessing these two properties has been discovered by Ludwig and Cyon (N. depressor). It arises from the vagus and the superior laryngeal nerve, and terminates in the heart muscle itself. It is believed that vasodilatation and depression of blood-pressure follow its stimulation and LangendorfT hints at the possible existence of a vasodilator centre.

(c) Spinal and Peripheral Vasomotor Centres. — The chief regulating influence of the bloodvessels lies in the vasomotor centre, whose duty it is to assume charge of all bloodvessels. The work of this centre, is, so to speak, apportioned out among lesser vasomotor centres, which regulate the activities of local vascular fields, and whose seat is in the thoracic portion of the spinal cord. This seems to be definitely proven, inasmuch as the lowered blood-pressure which follows division of the medulla, rises again, and disappears entirely when the spinal cord is destroyed. These spinal centres are excited by dyspneic and reflex stimuli but to a much less degree than the medullary centres.

1 Journal of Phys., vol. xxv, p. 49.

2 Sitzungsber. d. k. k. Akad. der Wissensch., Wien, 1890, Band xcix; Abt. 3, and 1894, Band ciii, Abt. 5.

3 Zentralbl. f. Phys., 1906-7, vol. xx, p. 872.

4 Arch, fur die ges. Phys., 1909, cxxviii, p. 1.

s Arch, fur Anat. und Physiol. Phys., Abt., 1903, p. 82.

Goltz and Ewald have shown that the arterial tone is reestablished even after almost complete removal of the spinal cord, and it is believed that in addition to the central and spinal centres there are peripheral centres located either in the sympathetic ganglia or in the vessel walls themselves.

(d) Anatomical Consideration of Vasomotor Nerves. — According to the newer division of the nervous system into the autonomous and vegetative, whereby the former comprises the nerve distribution to the motor (muscle) portion of the anatomy, and the latter the organic portion, the vasomotor nerves fall in the class of autonomous nerves. The vasoconstrictor fibers arise in the spinal cord, and leave it through the anterior root, running in the white Rami communicantes to the gangliated cord. The cerebrospinal fiber as such, never reaches the organ, but becomes merged in the sympathetic nerve, whose termination in the organ is a sympathetic neurone. The following table gives the point of exit of nerves supplying various portions of the body :

Head: First to fifth dorsal vertebras, especially second and third. Upper extremity: Fourth to ninth dorsal vertebrae. Lower extremity: Tenth to eleventh dorsal to third or fourth lumbar. Abdominal organs: Fifth dorsal to third lumbar; kidneys especially eleventh to thirteenth dorsal.

Lungs: Second to seventh dorsal, especially third to fifth dorsal.

The vessels of the head are governed by the vasomotors in the cervical sympathetic, and destruction of the upper cervical ganglia is followed by dilatation of these vessels. Stimulation is followed by pallor, a phenomenon often observed in man. Vasomotor nerve supply to the lungs is a matter of some dispute, Wood claiming that there are pulmonary vasomotor fibres. The heart muscle receives constrictor fibers through the vagus, while the sympathetic carries dilator fibers for the coronary arteries.

All the abdominal organs receive vasoconstrictor fibers through the splanchnics, and it is for this reason that the splanchnic nerve is the most important pressure regulating nerve in the animal economy.

Chapter II. Venous Pressure And Capillary Pressure

I. VENOUS PRESSURE.

Although the study of arterial blood-pressure has dominated the interest of clinicians, it is perfectly comprehensible that it is, after all, but one of the many factors of blood-pressure, and that capillary, and especially venous pressure, should not be wholly neglected. The reason why venous pressure in man has not been more generally studied, is because of the lack of a method applicable to general clinical use. Simplified methods and more detailed study with accurate instruments will doubtless furnish much information of clinical value. In this chapter an attempt will be made to review the more important methods devised for determining venous pressure.

A method of estimating venous pressure by means of weights was described by Frey. 1 His idea was to compress the veins by the use of gradually increasing weights, in much the same way as one uses the fine chemical balance. The pressure read would equal the number of grams necessary to compress the vessel.

In a later paper 2 he describes a simple instrument, consisting of a piston with a spring plunger. The end of the syringe-like arrangement is placed on the vein of the arm held on level with the right third rib, and one reads off on the scale in the barrel of the syringe the amount of pressure in grams. The pressure in health is given as 10 to 15 grams.

Gartner 3 devised a method for estimating the pressure

1 Deutsch. Arch, fur klin. Med., 1902, lxxiii, p. 511.

2 Medizinische Wochen., 1904, p. 77. s Munch, med. Woch., 1903, p. 2038.

VENOUS PRESSURE 31

in the right auricle. He suggested that the veins might be regarded as a manometer tube whose termination is in the right auricle, and he believed that, when the arm is slowly raised, the level at which the veins on the hands disappear, measured above the fifth rib (site of the right auricle), will give the pressure. In health the veins collapse when the hand attains the level of the fifth rib, therefore venous pressure is nil. In cardiac insufficiency, the arms must be raised higher to cause collapse of the veins. As ingenious as this method is, it possesses many fundamental weaknesses which do not make its usefulness an assured fact.

Oliver, and later Sewall 1 used a spring blood-pressure gauge. By this method pressure is exerted on a superficial vein, which is then milked toward the heart. The pressure is slowly released until the milked portion is seen to fill. At this instant the pressure is read off by noting the tension of a spring previously calibrated against mercury. Hooker and Eyster make objections on account of difficulty of calibration and the likelihood of mechanically raising the venous pressure distally.

The first to use air pressure was von Basch. 2 He employed for this purpose a modification of his instrument devised for estimating capillary pressure. The same principle was used by Recklinghausen 3 in an ingenious but complicated modification, with a transparent pneumatic pelotte. He found that the pressure was practically zero.

Following their leads, Hooker and Eyster 4 introduced an aluminium frame, so cut as to fit the arm, and closed below by a thin rubber sheet with a rectangular opening, and above by a glass plate. The opemng in the rubber dam is placed over the vein, and by raising the pressure in the box, the vein is collapsed, the amount of pressure required to bring this about, being read in centimeters of water. With their method, the normal venous pressure averaged 8 cm. In

1 Quoted by Hooker and Eyster.

2 Wien. med. Presse, 1904, p. 961.

3 Arch, fur Path, und PharmakoL, 1906, Iv, p. 468. * Johns Hopkins Hosp. Bull., 1908, p. 274.

32 VENOUS PRESSURE AND CAPILLARY PRESSURE

some cases of heart disease this was greatly raised. Accurate determination of blood-pressure is impossible when there is phlebosclerosis, a condition which Hooker and Evster met with quite frequently. y

By far the best method is the one described by Moritz and v. Tabora.^ This is based on the principle, that if a communication is made between a vein and a manometer tube filled with water, the fluid in the latter will flow into the vein until the pressures in both become equivalent. 1 he patient is placed in a horizontal position, the right arm is abducted to a right angle, slightly flexed at the elbow and the hand brought in a position of half pronation. This is the position least likely to cause obstruction to the flow 01 blood m the veins.

A bandage is tied around the upper arm, and, observing the usual aseptic precautions, a needle is introduced into the vena mediana, and some blood withdrawn in order to see if the ran has been entered. The needle is then connected with a tubing filled with an antispetic solution (1 gram chmosol m 2000 c.c. sterile Ringer's solution) and the fluid allowed to flow into the vein until it stops, at which point the venous pressure is read off, this being the point where the pressure in the veins and the pressure in the manometer are equalized.

This method is undoubtedly very exact and occupies no more time than does an ordinary intravenous injection and in the hands of Moritz and v. Tabora no unpleasant complications have arisen. The normal pressure corresponds to 40 to 80 mm. water, and the upper limit of normal they place at 80 to 100 mm. water. In pneumonia with decompensation the highest value was found, namely, 320 mm water When fully compensated, heart diseases show normal blood-pressure, but with signs of decompensation a rise is seen. In health, exertion causes a decided rise which is even more pronounced in decompensating cardiac lesions. The only valid criticism which one can make to this method is, that it is applicable only in the clinic, and its use is absolutely precluded in the consulting room,