Vital Capacity of the Lungs.-Deficiency.-Little Value of this Test.-Modes of ascertaining vital Capacity.-Hutchinson's Spirometer employed at the Hospital.-Hutchinson's Table.-Variations of vital Capacity in Persons of same Stature.-Instrument valuable chiefly as a negative Test.-Resistance of Chest to Pressure.

Ar an early period of phthisis, the amount of air which can be drawn into the lungs by a forced inspiration, and the amount that can be forced from the chest by a full expiration, is materially reduced. This diminution proceeds with the progress of the deposition of tubercle, and even with the expectoration of it, and the formation of cavities. The cavities. which form in a solidified mass, though they admit air, do not coincide with an additional general air capacity, for they seldom admit much, in consequence of costal pressure, and of the operation of contracting fibrous exudation, and their formation is for the most part co-ordinate with the further deposition of tubercle in other parts of the lungs, and the hepatization of intercurrent pneumonia.

As soon as tubercle has filled up a considerable number of vesicles, it is clear that the amount of air that may be inspired must be reduced, and this reduction of vital capacity, as with some impropriety it is styled, may be detected, if a careful experiment be made, ere percussion has become sensibly affected, or ere the respiratory sounds have become harsh or locally deficient.

The fact is obvious that the so-called vitality capacity must be reduced at a very early stage of phthisis; but as we have no means of ascertaining to a nicety, or even to a close approximation, the precise amount of capacity that is normal for the individual, we are at fault when we desire to know whether a certain not materially deficient capacity be unhealthy. The capacity varies in health to a considerable extent. The general range of capacity that is normal includes many degrees of deficient capacity in individuals, depending upon disease. Indeed, the normal range descends as low as the abnormal range of capacity in a considerable proportion of examples of phthisis, in the early part of the first stage, even when the respiratory sounds are assuming the phthisical characteristics. One male of 5ft. 8in. in height, will expire 220 cubic inches, while another of the same stature will expire

only 180 cubic inches; while I have ascertained that some persons of the same stature, in the early part of the first stage of phthisis, with altered percussion sound, and the phthisical respiration sounds, will expire not less. Taken alone, reduced vital capacity, if moderate, is of little value as a diagnostic sign of disease generally. It is of still less value as a sign of phthisis in particular. But if associated with altered percussion, harsh and deficient respiration confined to one apex, it is a somewhat valuable element in the body of evidence. It serves as a fair corroboration of the other physical signs. Deficiency of vital capacity is common to many other diseases. It is observed in bronchitis, in emphysema, in hepatization, in asthma, in cancer, in empyema, and in many diseases of the heart.

To be of any value as evidence of phthisis, the reduced capacity must be constant. If occasional only, it does not depend upon disorganisation. Deficiency of vital capacity, besides being common to many diseases, and being frequent as a natural condition, and dependent upon many physical and even moral influences of a strictly temporary character, possesses this disadvantage as a diagnostic sign of phthisis, that it points to no part of the pulmonary structure, to the apex or the base, or to the right lung or to the left, as the seat of tubercle, and therefore in these respects it comes in point of value much behind the signs of percussion and respiration, which not only denote tubercle, but indicate with exactitude, its precise situation.

The amount of expired air may be readily measured by breathing through a tube into a jar filled with water, and inverted over water in a reservoir, and so graduated as to denote the quantity of air which is received. But the measurement of the expired air is best effected by means of the spirometer of Dr. Hutchinson, and that of Mr. Coxeter. Dr. Hutchinson's instrument has been employed by myself in making the observations which are here recorded. An account of this instrument will be found at a subsequent part of this work. It is in constant use at the Hospital for Consumption. Every patient on admission, who is able to undergo the unavoidable fatigue, is made to use this instrument, and his vital capacity, as it is called, is ascertained and carefully recorded. However, it is but right to say that very little weight is attached by any of my colleagues, as far as I know, or by myself, to this test, and that we regard it in diagnosis as of infinitely less importance than percussion and auscultation, either singly or together.

When tubercle is very fully deposited in the lung, the vital capacity is notably diminished. Dr. Hutchinson has formed the following valuable tabular estimate of the vital capacity in the first stage of phthisis; but I am of opinion that the patients whom he examined were in an advanced part of the first stage, and that in some of them the disease was present in both lungs, and invading more than the upper lobes. Without the very slightest idea of impugning the diagnostic skill of Dr. Hutchinson, to whom we all are much indebted, knowing from much experience that some cavity signs are frequently absent for a time, I am strongly of opinion that a few at least of the cases regarded by him as having been only in the first, were in reality in the third stage of the disease. I have myself, on the first examination of many patients, found abnormal signs belonging to the first stage only, and on a subsequent examination a few days after, I have heard the conclusive cavernous respiration and the conclusive cavernous gurgling sounds.

For the purpose of more easy comparison with the healthy standard, as given by Dr. Hutchinson, I have placed the vital capacity of the first stage of phthisis, as given by the same authority, in juxtaposition with the natural or healthy estimate:

I have found that some few persons of very different stature have expired the same amount of air, even when none of the results could possibly be referred to nervousness or to inacquaintance with the operation of the instrument. Thus two medical men, well accustomed to the use of the spirometer, have breathed out the same amount of air, though their stature was respectively 5 ft. 4 in., and 5 ft. 8 in. The amount expired was in each case 220 cubic inches.

THORACIC ARTERIAL MURMURS.

105

The evidence of the spirometer, judged of simply by the above table, is only a very rough test of phthisis. If employed in the early period of the first stage, the instrument would doubtless detect a diminution, though a small one, of the vital capacity.

It may be observed, in respect of this test, that as far as phthisis in its first stage is concerned, diminution of capacity by itself is of little value, but that excess on the normal amount, as established by Dr. Hutchinson, is of great negative diagnostic value, for under these circumstances we never find phthisis, and seldom any other disease of the lungs, or indeed of the respiratory organs. This negative value is very satisfactory in that not very small class or group of cases in which we have gradual wasting of the body with hectic symptoms, marked with shortness of breath and some little cough, which presents itself to the physician, and in which no phthisical physical signs are made out. If we find the vital capacity to be natural, or nearly so, we may conclude that the disease is not phthisis.

The resistance to the pressure of the fingers, offered by the thorax, is, in some cases of phthisis in its first stage, sensibly increased; but this is never perceived until the auscultatory and percussion signs are unequivocally developed. This increased resistance is much more a sign of phthisis in the third than in the first stage of the disease.

CHAP. XVI.

FIRST STAGE-continued. ASCULTATION resumed.

Thoracic arterial Murmurs.-Influence of the respiratory Acts.-Influence of Force of cardiac Contraction.-Occasional Absence.-Little Value of this Sign.-Causes of it.-Loudness of cardiac Sounds.-Value of it.-Mechanism.-Comparative Power of solid and aeriform Bodies to acquire Sound from solid Bodies.-Adventitious Heart Sounds.-Venous Humming.

A PHYSICAL sign, remarkable in its character and readily audible, occasionally attends the first stage of phthisis. It consists of a gentle blowing arterial murmur at the apex of the chest. It may proceed from the pulmonary artery, the left subclavian artery, or the innominata on the right side. It seems to arise from the consolidated tuberculated lung pressing upon these vessels. The murmur or blowing is always

systolic. The pulmonary artery, in my experience, has been the most frequent seat of this sound; the left subclavian, and the innominata give out this sound considerably less often, and they (the two last-named vessels) are the source of it in nearly equal frequency. When the pulmonary artery gives out this sound, it is heard over a small nearly circular area of about one and a half and two inches in diameter, of which a point about half an inch from the sternum, and in the middle of the second costal interspace, is the centre. Beyond this range the pulmonary artery murmur, so originating, is very seldom heard. On a few occasions it has extended an inch beyond this area, in an oblique direction upwards and outwards towards the outer extremity of the clavicle. It is never heard at the apex of the heart, or in the direction of the apex of the heart. The murmur when proceeding from the left subclavian is higher, and is heard loudest at the first costal interspace near the sternum; it seldom or never reaches to the neck. When the innominata is the seat of the blowing murmur, it is heard on the right side of the sternum at the first costal interspace, and may be traced up to the clavicle in an oblique direction, passing outwards and upwards. It is rarely heard above the clavicle. The intensity of the sound is not uniform; it varies with the force of the heart, as do most other arterial murmurs; but the variation that is most remarkable is that which holds with the different acts of respiration. It is rare to hear a murmur arising from the pressure of tuberculated lung, that is not affected in its intensity by some one condition of the respiratory function. The condition that intensifies may be inspiration, a very full inspiration, a very full inspiration with the breath then held, or it may be the act of expiration. In the first stage of phthisis, I have found that the inspiratory act is generally attended with a slight increase of sound. But the greatest intensification, and it is really remarkable, is obtained when after a full inspiration the breath is held. It would appear that the conditions for the generation of the sound are now at their maximum. The tuberculated lung is, as far as possible, filled out and made to press upon the artery, while the heart beats with unwonted force, and propels the blood with energy through or into the compressed vessels, enlarging them beyond their normal size. In some examples of this arterial whiff or murmur, I have heard the sound only during the act of expiration; but this has been less common in the first than in the third stage.

This sign is made out in about five per cent. of cases of