Blood pressure in general practice

Introduction

In issuing this volume it is the aim of the writer to furnish to the general practitioner and surgeon a short treatise on blood-pressure entirely from the standpoint of its practical significance and value.

So recent is the whole subject of blood-pressure, its significance, the means of determining it, and its clinical use, and so extensive is the literature on blood-pressure published mainly in journals and magazine articles, that the busy general practitioner in many cases has not been able to learn the methods of its use and application in clinical medicine.

With this in mind the author has reviewed the literature on this subject, utilizing only such materials as he deemed of clinical value, avoiding what are as yet purely theoretic findings.

vi INTRODUCTION

This treatise therefore starts with the assumption that the writer is dealing with a new subject, and an effort has been made to present the material given in as simple a manner as possible.

In the text references have been omitted, but at the end a number will be found for those desiring to study the subject further.

The entire subject has been expressed as concisely as possible, and to some it may seem dogmatically treated and much material to have been omitted ; but the author, in extenuation, wishes to state that this is not intended to be an exhaustive treatise on blood-pressure, but a simple exposition of the subject easily grasped and from a clinical standpoint.

To facilitate ready reference the diseases with changes in blood-pressure have been arranged in alphabetical order, under the general headings of hypertension and hypotension.

If this simple volume shall aid the general practitioner to a better understanding of the methods of determining the princi-

INTRODUCTION vii

pies and some of the practical applications of blood-pressure determinations its mission will have been fulfilled.

I wish to express thanks to Dr. Wendell Eeber for his kindness in reviewing the section on the diseases of the eye, making this section as condensed as possible, but at the same time giving all the essentials for the general practitioner.

Contents

PAGE

Introduction v

CHAPTER I General Consideration and Technique

Historical review 1

Importance of blood pressure, and conditions

to which it applies . . . . 4

Definition of blood pressure 7

Methods of measuring blood pressure:

(1) Palpation 8

(2) Auscultation 9

Auscultatory blood pressure, sounds, and phases 11

Auscultation method, on what based 13

The inertia of mercury, and the relation of the

oscillation of the column to the accuracy of

the readings 14

CHAPTER II Blood Pressure Instruments

Choice of an instrument 17

Instruments: 18

(1) Mercurial.

(2) Those using other fluid media.

(3) Aneroid, spring-diaphragm, or dial.

ix x CONTENTS

PAGE

Instruments {Continued) :

(1) Mercurial 18

(a) Reservoir type 19

Examples described, "Cook" and

"Stanton."

Summary.

(b) U-tube 21

Example described, "Janeway." Summary.

(c) Closed tube mercurial 22

Summary.

(2) Instruments using fluid media other than

mercury 23

(3) Aneroid, spring-diaphragm, or dial in-

struments 23

Discussion of.

Nicholson apparatus 26

Description of 27

CHAPTER III Basic Factors on Which Blood Pressure Depends, Diastolic and Pulse Pressure, and Normal Readings.

Main factors 38

(1) Cardiac strength.

(2) Peripheral resistance.

(3) Elasticity of vessel walls.

(4) Volume of blood.

Discussion of.

Pulse and diastolic pressure 41

Normal range of pulse pressure.

Rule to estimate diastolic pressure (Brun-

ton).

General discussion of.

Importance of diastolic and pulse pressure.

CONTENTS xi

PAGE

Normal blood pressure readings 47

Adults.

Children.

Low limit.

CHAPTER IV Physiological Variations in Blood Pressure

Location of cuff 50

Position of patient 50

Meals 51

Sleep 51

Exercise 51

Nervous and mental stimuli 52

Altitude 52

Cardiac cases.

Phthisis.

Summary 54

Edema 55

Asphyxia 55

CHAPTER V Hypertension

General discussion of 56

Diseases with hypertension:

Angiosclerosis 59

Angina pectoris 60

Arteriosclerosis 61

Autointoxication 66

Diabetes 67

Drugs : 67

Adrenalin, 68; cocaine, 68; camphor, 68; digitalis, 68; normal saline solution, 69; strychnia, 69; atropine, 70; caffein, 70; tea and coffee, 70; ergot 70 xii CONTENTS

PAGE

Diseases with hypertension {Continued) :

Epilepsy, idiopathic 70

Exophthalmic goiter 71

Eye diseases: 71

Spasm of the retinal vessels, 73; cataract, 74; chronic interstitial nephritis in relation to the eye, 75 ; glaucoma, 76; retinal hemorrhage. . 76

Gout 77

Heart disease: 77

Aortic regurgitation, 77; chronic cardiac hypertrophy, 78; cardiac valve lesions other than aortic, 78; heart with loss of compensation, 79; myocarditis, 79; acute endocarditis, 81; bradycardia, 81; cardiac

arrhythmia 81

Increased intracranial tension : 82

Apoplexy, cerebral thrombosis, depressed fracture of skull, fracture of the base, Jacksonian epilepsy, intracranial hemorrhage, tumors

(rapid growing cerebral) 82

Nephritis: 83

Chronic interstitial, 84 ; chronic parenchymatous, 85; acute nephritis, 85;

uremia 86

Obstetrics and eclampsia 86

Plumbism 89

Treatment of hypertension : 90

Prophylactic, general, vasodilatation, and other measures 90

CONTENTS xiii

Chapter VI Page

Hypotension.

Definition and general consideration of 105

Diseases with hypotension:

Acute cardiac conditions and pericarditis 106

Chronic wasting diseases: Cancer,

chronic phthisis, anemia 106

Diseases with a marked loss of fluid: Cholera, diarrhoea, dysentery, and after profuse vomiting, as in carcinoma of the stomach, intestinal

obstruction, and peritonitis 106

Drugs: Alcohol, tobacco 107

Hemorrhage (extensive) 108

Acute infectious diseases :

Diphtheria, 109; pneumonia, 109; rheumatism (acute articular), 112; scarlet fever, 112; typhoid fever, 112; acute

infections of children 115

Neurological conditions:

Alcoholic delirium, 115; insomnia, 116; acute mania, 116; melancholia, 116; neurasthenia, hysteria, etc., 116; general paresis, 116; trifacial neuralgia 117

Phthisis 117

Shock and collapse 118

Syphilis:

Acute 119

Tabes dorsalis 119

Treatment of hypotension 120 xiv CONTENTS

Chapter VII Page

Surgery and Anesthesia.

Ether 121

Nitrous oxide 121

Chloroform 121

Spinal anesthesia (cocaine) 122

Operative procedure 122

CHAPTER VIII Life Insurance

Statistics 127

Importance of blood pressure readings in 128

Factors to be considered 129

Special cases 132

LIST OF ILLUSTRATIONS

PIG. PAGE

1. Auscultation Method 8

2. " Cook " Sphygmomanometer .19

3. "Stanton" Sphygmomanometer 20

4. " Janeway " Sphygmomanometer ........ 21

5. " Rogers " Sphygmomanometer 24

6. " Nicholson " Sphygmomanometer 26

7. New Nicholson Pocket Sphygmomanometer partly

open 29

8. New Nicholson Pocket Sphygmomanometer fully open 32

9. New Nicholson Pocket Sphygmomanometer sectional

view 34

10. Blood Pressure and Temperature Chart 52

BLOOD PRESSURE IN GENERAL PRACTICE

Chapter I General Consideration And Technique

HISTORICAL.— Going a little into the history of blood-pressure determination we find it dates back to 1828, when Poiselli introduced the first U-tube mercurial manometer.

Shortly after Ludwig devised the Kymographion, a manometer connected directly to an open artery, and recording on a revolving cylinder; but it was not until 1876 that a useful apparatus for estimating blood-pressure in man was used by Marey, by which he could determine both systolic and diastolic blood-pressure. There was, however, no general use of blood-pressure apparatus until some eleven years later (1887), when v. Bosch brought forward his apparatus, consisting of a small rubber bulb filled with water and connected with a mercurial manometer; the bulb being pressed upon the radial artery until the pulse was just obliterated, and the pressure read off the manometer, v. Bosch later modified his apparatus by using an aneroid in place of the mercurial manometer.

V. Ptoin further substituted on the v. Bosch apparatus air in place of water, which was a great advance, but both instruments have a large possible error, which Tigerstedt claims has reached 78 mm.

All our modern apparatus dates from 1896, when Riva-Rocci, in Italy, used a rubber bag, 5 cm. wide, surrounded by an inelastic material, completely encircling the arm. This cuff was connected by rubber tubing with a reservoir of mercury having an upright capillary tube, alongside of which was a mm. scale. Air was pumped into the cuff, compressing the brachial artery until the pulse below the band was obliterated, and then, by releasing the air slowly, he determined when the pulse reappeared and thus obtained a reading of the maximum or systolic pressure, shown by the column of mercury in the capillary tube.

All instruments which give accurate readings have utilized the principle of the pneumatic constricting band, except that now the width of the cuff is at least 12 cm., as the narrow cuffs, such as the original Eiva-Eocci, give too high readings. This very important error was shown by the work of v. Eecklinghausen to be due to the loss of pressure in compressing the tissues, and that it could be eliminated if a cuff from 12-15 cm. wide were utilized. Dr. T. C. Janeway states he has found in high-tension cases a 5-cm. cuff to register as much as 60 mm. higher than a 12-cm. cuff.

All our modern blood-pressure determinations, as on the Riva-Eocci instrument, are recorded as the pressure measured by the height of a column of mercury of so many mm., or, in other words, mercury is the standard on which blood-pressure readings depend.

The Importance of Blood-pressure and Conditions to Which It Applies.— The whole subject is one which has become prominent from a practical standpoint, in this country in about the last eleven years, though it had its beginnings as far back as 1828 in Europe.

It has been, however, only in the last five years that the importance of accurate blood-pressure readings in their diagnostic, prognostic, and therapeutic application to general medicine has begun to be appreciated, and their value realized by the general practitioner.

Blood-pressure determinations are now of so well recognized value in medicine and surgery, that one of the important questions of to-day is what are their application and meaning in special conditions, and how reliable are they when other means fail us.

Dr. T. C. Janeway has very clearly expressed the matter in a recent article, "When Should the General Practitioner Measure Blood-pressure?"

He says, in substance, it should be taken:

(1) In the first examination of every patient.

(2) Occasionally for watching the progress of cardiovascular disease and nephritis.

(3) Examination for certifying to the state of health : in life insurance • in applicants for the army, navy, police, fire department, and in schoolboys engaged in athletics ; and he also mentions eclampsia and diagnosis in conditions with abdominal pain.

In addition Briggs and Cook show blood-pressure determinations to be one of the most important aids in diagnosis and treatment of eclampsia and cardio-renal disease, and their undoubted value, in typhoid fever, in medication of children; in surgery before, during, and after operative procedures, and in injuries of the head, etc.

In a paper on diagnosis read before the Michigan State Medical Association Dr. Richard C. Cabot says: "The next procedure, following my personal routine, is the examination of blood-pressure. That leads me to say something about the value of blood-pressure in physical diagnosis. If I were allowed to have only two instruments of precision for my aid in physical diagnosis, they would be the stethoscope and the blood-pressure machine.

"I have been saved from wrong diagnoses and put on the track of right ones more often by that machine than anything else I know of, except the stethoscope. And I am speaking now, as I spoke all along, by the check of the autopsy.

"I regard the measurement of blood-pressure as the most important of all the resources that have been added to our armamentarium as physicians, in the last fifteen years.

"The measurement of blood-pressure,

IN GENEEAL PEACTICE 7

when you are familiar with the method, can be made in a minute and a half perfectly well."

Blood-pressure determinations are of value to the specialist in eye and ear conditions ; in fact, there is no branch of medicine in which blood-pressure is not significant, and often an aid when other means of diagnosis have not been sufficient.

Definition.— By blood-pressure is meant the arterial tension or pressure of the blood in the vessels within which it is contained.

Systolic and Diastolic. — Blood-pressure is divided into the maximum or systolic pressure and the minimum or diastolic. The systolic is the greatest pressure exerted and takes place during systole of the heart; the diastolic is the lowest pressure, and occurs in the cardiac cycle just at the beginning of the systole, or at the end of the diastole, the time when most of the blood has passed on through the capillaries into the veins.

Pulse Pressure. — From these we obtain

11 pulse pressure," which is the difference between the diastolic and systolic pressures.

Mean Pkessure. — Mean pressure is about the average between the systolic and diastolic readings, but has little clinical value and is seldom used.

Methods of Measuring Blood-pressure.— The apparatus being set up ready to operate the pneumatic cuff is adjusted snugly, and without compression, to either the arm or the thigh, usually the arm, taking care that the cuff is at the level of the heart. The cuff is then inflated until the pulse below the constriction is obliterated, which is determined by palpating the artery. The estimation of blood-pressure is then made by either one of two methods: (1) The old or Palpation Method. (2) The new or Auscultation Method, described in 1905 by Korotkow.

Palpation Method. — (a) Systolic. — After obliterating the arterial pulsation in the vessel below the cuff, slowly release the air pressure, allowing the mercury to

Fig. 1. — The auscultation method.

IN GENEEAL PRACTICE 9

fall evenly, and note the height of the column when the pulsation reappears to the palpating finger. This gives the systolic or maximum pressure, and will be found easy to obtain on all instruments.

(b) Diastolic. — After taking the systolic pressure allow the mercury to fall slowly, and note the varying degrees of oscillation of the mercury column. Eead the scale at the base of the maximum fluctuation and it gives the diastolic pressure.

Or when the first change from a small to a full bounding pulse is noted read the height of the mercury column, and it gives the diastolic pressure.

Both methods of determining the diastolic pressure are very unreliable and not accurate nor practical in general practice.

Auscultation Method. — This is an accurate method for both systolic and diastolic determinations. — ( a ) Systolic. — As in the palpation method, having inflated the cuff until the pulse is obliterated, place the bell of an ordinary binaural stethoscope over the artery just below the cuff. Now release the air pressure slowly and listen with the stethoscope. When the first cardiac beat passes the constricting cuff a loud, clear thump is heard and the true systolic pressure is obtained by reading the height of the mercury column.

(b) Diastolic. — In taking the diastolic pressure continue to release the air and listen over the artery. The thumping sound is followed by a murmur, and then by a second thumping sound, which becomes fainter and suddenly disappears. At the time the second thumping sound becomes fainter, again note the height of the mercury column, which gives the true diastolic pressure.

This last auscultation method has almost revolutionized the determination of blood-pressure, for the diastolic pressure can be as easily and accurately determined as systolic pressure, a result impossible to attain in the past, there being such a large personal element in obtaining the diastolic pressure that most observers did not attempt it.

The diastolic and pulse pressure (difference between systolic and diastolic) are thus accurately determined by this method, and are often of even greater importance than the systolic.

Auscultatory Blood-pressure, Sounds and Phases.— Placing a stethoscope over the brachial artery just below the constricting cuff and releasing the air pressure slowly, you hear five distinct phases in most all cases.

(1) A loud, clear thump is heard as the first wave of blood passes the constricting cuff, which gives the systolic pressure by reading the height of the mercury column.

(2) In a short time the first phase is followed by a murmur, which lasts for a variable period, and constitutes the second phase.

(3) After the murmur a loud, clear thump is again heard, constituting the third phase, often louder than the first phase.

(4) Then the third phase passes into the fourth, which is simply a duller sound similar to the third and is probably produced by the return of the blood vessel to its normal caliber as the air pressure is lowered.

(5) The sounds in the fourth phase gradually become fainter until you have the fifth phase or the disappearance of all sound. The end of the third phase or beginning of the fourth phase gives the true diastolic pressure.

At the present time there has not been enough work done on the intensity of the sounds of the various phases or their relative lengths in mm. of mercury to give any positive findings, though much suggestive work has been done along this line. The intensity of the sounds of the third phase being considered of importance in determining the cardiac strength, a loud clear sound indicating a strong heart and vice versa.

The main information at present obtainable from the auscultation method is the determination of accurate systolic and diastolic pressures and from them the

IN GENEEAL PEACTICE 13

pulse pressure, by the simple process of subtraction, e. g.

Systolic 160 mm. Hg

Diastolic 120 mm. Hg

Pulse pressure 40 mm. Hg

Of pulse pressure and diastolic pressures I shall have more to say later.

Auscultation Method, on What Based. — In the auscultation method it is largely a question of the physics of fluids, e. g., the artery is constricted by means of the pneumatic cuff; below it there is no arterial flow, and the vessel walls are in a semi-relaxed condition. The air pressure in the cuff is lowered gradually until the heart has power enough to drive some blood into the relaxed vessel beyond. The sudden flow of blood into the relaxed vessel sends the wall into vibration, and a loud, clear thump is heard, which gives the systolic pressure. In making the diastolic estimation there again is a physical condition of a fully expanded artery above the pneumatic cuff, a constriction under the cuff, and an enlargement below. Fluid passing from a large tube through a constriction into a large opening makes a murmur, exactly what takes place, and when the caliber of the tube is uniform, or, in other words, when the diastolic pressure is able to overcome the constriction of the cuff, there will be no longer any loud sound. It can easily be seen that it makes no difference whether the mercury column records each pulsation of the heart or not, but that it shows much more easily and accurately the correct blood-pressure than coidd be read if it tvere fluctuating very actively.

The Inertia of Mercury and the Relation of the Oscillation of the Column to Accuracy of Readings. — Here I wish to make clear a point which has created considerable confusion in the past, the relation of the inertia of the mercury column to the determination of the diastolic pressure, and also as to whether it is of importance for the column of mercury to fluctuate with each pulsation of the heart. Were we to adhere to the old method of reading the diastolic pressure, the lowest point of the maximum fluctuation, the mercurial inertia might be of slight importance, but from a practical standpoint it is of little significance.

When we use the auscultation method for determining diastolic readings, a method now almost universally used, on account of its ease and accuracy, the lack of fluctuation of the mercury has absolutely no disadvantage. On the contrary, it becomes easier to obtain the true pressure reading, where the column is not actively oscillating, as is the needle of the aneroid.

Confusion has been brought into this subject of blood-pressure due to the erroneous idea having been advanced that the actual fluctuation of the mercury column, or needle of the aneroid, is essential, it recording each pulsation of the heart.

If pulsations are to be recorded it is better to employ a sphygmograph (where the pulsations could be preserved and interpreted, as they could not on a blood-pressure apparatus), but for the determination of blood-pressure the sphygmomanometer should be used.

To illustrate this, let us recall a little problem of physics : a pump forcing water through a pipe gives an intermittent flow. Placing an air-dome on the pipe line makes the flow continuous beyond the dome, but the pressure is equal on both sides. So blood-pressure determination is a question of iHe pressure existent in the arterial system, not of the pulsation of the heart.

Chapter II Blood-pressure Instruments

CHOICE OF AN INSTRUMENT. -- The number of instruments at present available for blood-pressure work is legion, and it is decidedly confusing to one entering this field to select a good practical instrument.

In his book, "A Clinical Study of Blood-pressure,' ' Dr. T. C. Janeway gives the following advice on the choice of a sphygmomanometer :

(1) " Manometer must be of such construc-

tion as to give permanently exact

readings.

No metal manometer yet invented remains accurate, hence this means the use of a properly graduated mercurial one.

(2) Compressing armlet must have a

width of at least 12 cm.

18 BLOOD PBESSURE

(3) Connections must be practically non-

distensible tubing.

(4) It must measure both systolic and di-

astolic pressure.

(5) Its application must be simple, and

require not more than two to three minutes.

(6) It must be at once substantial, light,

and compact, so that it may be easily and safely carried.

(7) It must not be too costly.' 9 Instruments.— Every apparatus for determining blood-pressure belongs in one of three classes, those using:

(1) Mercury.

(2) Some other fluid medium.

(3) The aneroid, spring diaphragm or dial.

(1) The mercury type is further divided into:

A. Those having a reservoir; the mercury rising in an open end capillary tube from a zero point and having a scale graduated in millimeters.

Fig. 2. — Cook's modification of the Riva-Rocci sphygmomanometer, showing narrow armband in place, with cautery bulb-inflator.

B. Those employing the U tube.

C. Those having a short straight tube

with a closed end.

Class A.— To this class belong the "Riva- Rocci," the "Cook," the "Stanton," and more recently the "Sands," a copy of the "Stanton."

I shall give you a brief description of the two simpler forms, the "Cook" and the "Stanton."

The "Cook" seen in cut No. 2 utilizes all the principles of the original Riva- Rocci instrument, consisting of a constricting pneumatic cuff connected with a mercurial manometer, and having a means of inflation. The cuff when applied over the brachial can be filled with air until the pulse at the wrist is just obliterated.

This is a fairly accurate instrument for determining systolic readings, but not having a good air release is not practical in determining diastolic pressures. It is inaccurate in that it uses a 5-cm. cuff, which gives too high readings.

Though by the use of a jointed tube it is fairly compact, the mercury is easily spilled and the instrument fragile. Its double bulb for inflation is also a constant source of annoyance from blowouts.

Now turning to cut No. 3 the original " Stanton" apparatus is seen, a reliable instrument, but no longer manufactured.

(1) It was a large, heavy instrument, using a 10-cm. cuff, which gave too high readings.

(2) It was not very portable, requiring to be taken apart and set up when used in general practice.

(3) It was difficult not to lose the mercury.

(4) It had the same defect as the "Cook" apparatus in that it used a double rubber bulb for inflation. However, it was largely adopted and gave accurate readings when a wide cuff was used.

All the instruments of this class have their drawbacks preventing their becoming practical portable instruments. Some require the manipulation of screws and washers; some are large and heavy to

Fig. 3. — Stanton's sphygmomanometer, showing arrangement of parts, with cautery

bulb-inflator.

Fig. 4. — Janeway sphygmomanometer, attached to arm, showing method of retention of cuffarrangement of momanometer, with Politzer bag inflator.

transport; in all the loss of part of the mercury cannot be prevented and the double rubber bulbs are constantly getting out of order.

They, therefore, are not instruments suitable for the general practitioner.

Class J5.— The U-tube instruments.

In this class are the " Janeway," "Martin, ' ' " Mercer, " " Brown, ' ' " Sahli, ' » "Faught^' and many others.

In the cut you can see the " Janeway,' ' which is one of the earliest and best known of this class.

This instrument has the advantage over many others, in that it uses an accurate 12-cm. cuff, and hence the readings are correct on most of the instruments.

(1) But in order to carry it, the end of the U-tube has to be closed with a cork, which is often forgotten and as a result the mercury is spilled.

(2) The mercury often escapes from the joint made on the long arm of the TJ tube.

(3) As made now, there is a wide metal union which obstructs the reading for some 30 mm. in the middle of the scale.

(4) Like all U-tube instruments the scale has to be condensed one-half to allow for the descent of one column while the other rises, so none can be read closer than two mm.

As glass tubing cannot be blown of uniform caliber there is often a swell in one limb of the manometer precluding the mercury from rising or falling equally in both sides and as one column is balanced against the other any error is multiplied by two. Two instruments recently examined were found to vary 40 mm.

Many of the U-tube instruments are too bulky to transport and the others which are shorter, using a jointed tube, have been condemned by many because a plug must be placed in the end of the tube to prevent the spilling of the mercury.

Class C. — In order to attain portability, a greatly desired feature in blood-pressure apparatus, several instruments have been made having a short closed tube with mercury working against the inclosed air, e. g., "Hertz," "Roger's Simplex,'' "Oliver."

These have failed because : ( 1 ) The scales have necessarily to be condensed, making the readings gross, and further this condensation greatly increases any error. (2) The scales have to be specially standardized by comparison with a mercurial column and, being fixed, cannot be adjusted to allow for any change in the compressibility of the inclosed air column, which varies greatly according to moisture, temperature, and climate.

Type 2. — (Instruments using fluid medium other than mercury). — These instruments are too long for portability where the open end tube is used or where the closed end tube, e. g., "Bendick air- water apparatus.' ' They have all the disadvantages of the closed end mercurial instruments.

Type 3. — (The aneroid, spring diaphragm or dial). — In addition there are the aneroids or spring diaphragm instruments, following the old model of the v.

Bosch apparatus. These, while convenient in some respects, as Dr. Janeway says: "Need to be standardized frequently by comparison with a mercurial manometer, which is irksome, and they are difficult of repair.

"Depending, as they do, on a spring they wear out and are not dependable. ' '

Their lack of dependability is clearly shown by Dr. J. W. Fischer, medical director of the Northwestern Life Insurance Company, when he says in a letter to his medical examiners: "The experience of this department with the various makes of sphygmomanometers has convinced us that the use of an instrument registering the blood-pressure with a mercurial column is preferable, although the spring or diaphragm instruments are satisfactory if occasionally checked up with a mercurial instrument. ' '

The spring aneroid, so-called diaphragm, instruments have solved the portability problem, but have added many inaccuracies, so they are not dependable.

Fig. 5. — Roger's sphygmomanometer adjusted to arm, showing atomizer bulb-inflator.

The elasticity of a solid is a variable quantity at the best. So in the aneroid or dial instruments the expansion and the contraction lessen the elasticity until no dependence can be placed on its reaction. To compensate for this loss of elasticity the manufacturers make the dial movable so the indicator can be set at zero ; * as the vitality of the drum or spring is permanently lessened, the needle does not give accurate readings at other points, and its condensed scale multiplies the errors.

The auscultatory method of obtaining the diastolic pressure is now well recognized as the only accurate and simple method. Here, where you are listening over the artery for the change of sound, if you observe the dial of an aneroid, the needle is showing wide excursions, making it impossible to determine the correct reading, you do not know what point in the excursion of the needle to note. This is not the case in a good mercurial instrument; the fluctuation is but slight. As diastolic readings are as impor-

* Recently one manufacturer has made instruments with the dial fixed, and as a result in many the needle does not come to rest on the zero point.

tant as, if not more so than, systolic, the fact that the correct diastolic reading cannot be obtained is a serious defect in this class of instruments.

Of these instruments Dr. Richard C. Cabot makes the following remarks in a paper on diagnosis: "The little instruments which are widely advertised as being very portable are splendid for the first few months, but if you do many high pressures on them, like any other aneroid instrument, they give out. The only reliable machines are those having a column of mercury, which is a bother to carry around, but which is necessary."

Finding the need for a reliable, accurate, durable, simple, portable, and inexpensive mercurial apparatus, the author has added one more to what might seem an already well-filled field.*

The instrument shown in cut No. 6 is

* Instrument described in Journal American Medical Association, July, 1911, and later imitated. But these copies are all liable to an error of from 10-15 mm. Hg on the high readings, due to the fact that they employ a much larger capillary tube than my original apparatus, and, as they use the same scale as mine, there is no allowance made for the change in bore of the tube employed.