Researches on the nature, pathology and treatment of emphysema of the lungs : and its relations with other diseases of the chest

Front matter

The Library of the Wellcome Institute for the History of Medicine

MEDICAL SOCIETY \ OF ioNDON DEPOSIT

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Preface

An extended inquiry into the anatomy of the human hmgs naturally led me to a consideration of their pathological conditions. Amongst the subjects to which my attention has been directed for some years past is emphysema. The conclusions at which I have arrived, with reference to the morbid anatomy, pathology, and treatment of the disease, are the result, not only of a careful examination of the structural changes it presents after death, but also, of a close study of its symptoms and progress during life. Some of the facts detailed in the following pages have been already in part presented to the profession : first, in a paper communicated to the Royal Medical and Chirurgical Society of London ; and, secondly, in one subsequently read before a section of the British Medic9,l Association. The opportunities of further investigation and study of the disease, which I have had since these papers were written, have tended to confirm the opinions therein expressed.

Hope Stkeet, Liverpool, November, 1862.

Contents

PEEFAOE

Chapter I. THE MOKBID ANATOMY OF EMPHYSEMA

Opinions of earlier Pathologists. Views of Laennec. Frequency of the Disease. Importance of a knowledge of the Minute Structure of the Lungs. Ultimate Pulmonary Tissue; its Arrangement and Sti-ucture. The different kinds of Emphysema. Vesicular Emphysema ; its various Forms. Modes of Preparation of Lung-Tissue for Examination. Changes which take place in the Air-sacs in the different Stages of the Disease. Condition of the Blood Vessels ; of the Bronchial Tubes. Interlobular Emphysema

C^aptjcr II.

THE PATHOLOGY OF EMPHYSEMA.

Importance of a Correct View of the Pathology of the Disease, in reference to Treatment. The Question of Degeneration of Tissue Considered. All Cases of Emphysema not to be included under the same Head. Distinction between Partial and General Emphysema. Mr. Eainey's View of Fatty Degeneration. Views of Dr. Williams and Dr. Jenner. Investigations of the Author. Constitutional Nature of the Disease ; its Hereditary Character, etc vi.

CONTENTS.

Page

(Cljaptei III-

THE DETERMINING CAUSES AND MECHANISM OF EMPHYSEMA.

Two Principal Theories of the Determining Causes of the Disease. Views of Laennec. Theory of Dr. Gairdner. The Mechanism of Kespiration. Effects produced by Collapse of the Lung. The Expiratory Theory. The Modus Operandi of Expiratory Efforts. The Anatomical Arrangement of the Walls of the Chest, and the Disposition of the Lungs. Effects of Forced Expiration. The Case of M. Groux. Eesults of the Author's Observations. Infrequency of the Disease as a Sequel of Pleurisy and Pneumonia; its frequent Occurrence in Tubercular Lungs. Cases recorded by M. Guillot. 36

Chapter IV.

THE SYMPTOMS AND PHYSICAL SIGNS OF EMPHYSEMA.

Dyspnoea and Cough. Haemoptysis. The Occurrence of Asthmatic Symptoms. Aspect of Patients. General Configuration of the Chest. Movements of the Chest in Respiration; their Variations in different Cases; Causes of these Variations. Character of Inspiration and Expiration, and of the Act of Coughing, Percussion and Auscultation. Character of the Respiratory Sounds. The Physical Signs and Symptoms referable to the Structural Alteration in the Lung-Tissue. Diminution of the Respiratory Function, and of the Quantity of Blood circulating in the Lungs. Diminished Temperature of the Body 54

Cljapte V.

THE SEQUELiE OF EMPHYSEMA, AND THE DISEASES ASSOCIATED WITH IT.

Bronchitis ; its General Characters ; Sources of Danger in Severe Cases ; Deposit of Fibrinous Clots in the Heart, etc. Asthma; its frequent Occurrence; Its Relations to Emphysema. Disease of the Heart; Parts involved ; Causes. Dropsy. General Cachexia and Anosmia. Extravasation of Air into the Areolai' Tissue of the Trunk. The Relations of Emphysema with Phthisis, etc 68

CONTENTS.

vii.

Pago

€^n^tx VI.

THE TEEATMENT OF EMPHYSEMA, AND OF THE DISEASES CONNECTED WITH IT.

Treatment Considered under Two Heads : 1st. Of the Disease itself; 2nd. Of the Secondary Consequences. General Principles of Treatment. Eemedies to he Used. Dietetic and Regiminal Treatment. Treatment of Bronchitis in its Acute Form. Cases. The Use of Turpentine in Severe Cases. Treatment of Chronic Bronchitis ; of Asthma ; of Cardiac Disease, Dropsy, etc. . . 85

LIST OF ILLUSTRATIONS.

PLA.TE I., Fig. 1.

Fig. 2.

PLATE II., Fig. 3.

Fig. 4.

PLATE III., Fig. 5.

Fig. 6.

PLATE IV., Fig. 7.- Fig. 8.

PLATE v.. Fig. 9.

PLATE VL, Fig. 10.

PLATE VIL, Fig. 11.

Air-Sacs of Healthy Lung (Adult Human). Do. Do. Do. (Infant).

Slice of Cat's Lung.

Do. Human Lung.

Air-Sacs of Emphysematous Lung.

Do. Healthy Lung.

Slice of Healthy Lung-Tissue.

Do. Emphysematous Do.

Air-Sacs of Emphysematous Lung.

Do. Do. Do.

Slice of highly Emphysematous Lung-Tissue.

PLATE I.

Fig. 1.

Fig. I is a drawing of a terminal bronchial tube, with a group of air sacs, or lobuleite, connected with it, divided transversely (human). a, the terminal bronchial tube; b, the dilated extremity of the terminal bronchial tube; c a c, individual air-sacs. At d, a bristle is seen passed into an air-sac ; oue end is seen opening into the common cavity in which the bronchial tube terminates. At e e are seen the openings of other sacs which lie beneath those which are exposed; six sacs are seen converging to the common centre. The markings in tlie air-sacs denote the boundaries of the alveoli.

Fig. 2.

Fig. 2 is a drawing of two terminal bronchial tubes, with two groups of air-sacs, or lobulettes. The terminal tubes are seen to pass from a bronchial tube (a], and they terminate each in a group of air-sacs, h, terminal bronchial tube; ceo, air-sacs; d d, openings leading to air sacs beneath those exposed. This dingram was taken from the lung of an infant under one year of a^e

PLATE II.

Fig. ;^

Fig. 3 represents a very thin slice of a cat's lung (injected, inflated, and dried), from the surface of the lung. The eye is looking upon the cut surface. The depressions, a a, are the bottoms of the air-sacs, I'esting on the pleura. The light coloured lines that surround them are their walls, and the small depressions seen within the walls, i b, marked off by less distinct lines, are the alveoli. The specimen from which this drawing was made was a very good one, and the drawing may be considered as fairly representing the appearance presented.

Fig. 4.

Fig. 4 is a drawing of a siniiliir slice to that of Fig. 3, taken from a human lung, a a a are the air-sacs, h b the alveoli. The lighter portions represent the walls of the air-sacs and the alveoli.

PLATE III.

Fig. 5.

Air sacs of a piece of emphysematous lung, injected, inflated, and dried. The lung from which the piece was taken was emphysematous along its margins. The piece was taken from the margin It shews dilatation of the air-sacs, more or less obliteration of the alveoli, and slight perforation. The black spots represent the perforations. The air sacs in the piece of lung examined varied in diameter from l-20th to l-30th of an inch — being more than double their ordinary size in health.

Fig. 0.

Air-sacs from the same lung as Fig. 5, but not emphysematous. The alveoli are shewn with their septa well marked. The diameter of the sacs in the part examined varied from l-45th to l-70tb of an inch. Figs. 5 and 6 were both taken by means of the camera lucida, and the same magnifying power was used in both. They therefore shew the relative size of healthy and emphysematous air-sacs.

PLATE IV.

Fig. 7.

A slice of healthy lung-tissue. It shows the openings of the divided air-sacs, and the walls separating them, in a healthy condition. No pei'forations are seen. (Taken by means of the camera lucida.)

Fis. 8.

Slice of emphysematous lung-tissue in the earlier stage of the disease. The black spots show the perforations in the walls of the air-sacs. (Taken by means of the camera lucida.)

PLATE V.

Fig. 0.

Air-sacs of emphysematous lung, as seen through dissecting microscope. The hristles are passed through the sacs. The upper walls of two, and the lower wall of one air-sac, are seen with their perforations.

PLATE VI.

Taken from a portion of lung very emphysematous. It shows the appearance of the air-sacs in a dilated condition, with their partitions much ruptured, and full of large perforations. (Drawn by means of the camera lucida.) The black spots shew the perforations. The cavities — the distended and broken-down air-sacs — in the piece of lung from which this was taken had a diameter of l-U>th,l-20th, and l-27th of an inch.

EMPHYSEMA OF THE LUNGS.

CHAPTER I.

THE MORBID ANATOMY OF EMPHYSEMA.

Opinions of earlier Pathologists. Views of Laennec. Frequency of the Disease. Importance of a knowledge of the Minute Structure of the Lungs. Ultimate Pulmonary Tissue; its Arrangement and Structure. The different kinds of Emphysema. Vesicular Emphysema; its various Forms. Modes of Preparation of Lung-Tissue for Examination. Changes which take place in the Air-Sacs in the dififerent Stages of the Disease. Condition of the Blood Vessels; of the Bronchial Tubes. Interlobular Emphysema.

Previously to the time of Laennec. pulmonary emphysema was for the most part considered by pathologists as produced by an infiltration of air into the areolar tissue of the lungs.* An imperfect knowledge of the anatomy of these organs led to the supposition that a rupture of the air-cells would give rise to extravasation of air into the tissue by which they

■■f- Descriptions of lungs which were large, and distended with air, and in some instances having dilated air-cells, will be found in the works of some of the earlier pathologists — Bonet, Morgagni, Floyer, Eusch, Valsalva, and Baillie ; but no true definition of the disease was given before that of Laennec.

B

EMPHYSEMA OF THE LUNGS.

were connected with each other. An improved anatomical knowledge and further pathological inquiry have shown us that the quantity of areolar tissue in the lungs is very small ; that extensive rupture of the air-cells may take place without infiltration of that tissue resulting; and that the only parts where such infiltration does occur are those in which the abovenamed tissue surrounds the various lobules.

Laennec was the first to draw the distinction between the two kinds of pulmonary emphysema ; viz., vesicular and interlobular. The former he recognised as consisting in a dilatation or distension of the ultimate portions of the air-tubes. Subsequent researches have tended to prove the correctness of the French physician's observations in this respect ; although the theory he advanced of the determining cause of the disease, as I shall have hereafter to show, has given way under an improved knowledge of the physiology of respiration, and more extended pathological inquiry.

Since the time when Laennec wrote, many able observers have directed their attention to this disease. Nevertheless, the information we possess with reference to it is insufficient to enable us to generalise with certainty on its essential nature ; and there are numerous points in connection with its pathology and determining causes, on which investigations are necessary, in consequence of the diversity of opinion which exists thereon.

Of the great frequency of the affection in varying degrees of severity, no one who has been engaged in

MORBID ANATOMY, extensive public or private practice can entertain any doubt;* and, considering the gravity of the symptoms the disease produces in its progress, and the tendency which exists for other organs to become secondarily involved, we cannot but admit the great importance of an early recognition of its symptoms, and a more accurate knowledge of its essential nature.

In speaking of the disease, Lebert has the following remarks in his Pathological Anatomij : — " Few diseases have given rise in the last twenty years to so many theories, so many explanations, more or less conjectural; and, as no one of them appears to us satisfactory, in the present state of science, it is the more essential to describe in a rigorously exact manner everything which relates to this affection, in order that for the future these materials may serve to estabhsh doctrines more generally satisfactory on the subject."

Again, writing on the same subject, Rokitansky observes: — "The conditions giving rise to the production of emphysema, and its pathogeny in general, although much labour has been devoted to the affection, are still far from clear." Further, Hasse, in speaking of the affection, and whilst admitting the influence of catarrh and hooping-cough as occasional causes of the disease, remarks: — "The character and real import of emphysema must, however, be

* In fifty-three cases of cholera examined by Louis, twenty-three of the individuals were found to be more or less affected with emphysema of the lungs, in various stages ; nor was there any ground for the assumption that it had become developed during the fatal malady.

EMPHYSEMA OF THE LUNGS.

admitted to depend on other causes, as yet not thoroughly made out."

These quotations will be sufficient to indicate the uncertainty which at present exists with reference to our knowledge of the nature and pathology of this affection.

To the study of morbid anatomy and pathology, a knowledge of minute structure is essential ; hence the rapid strides which these sciences have made since the microscope has revealed to us the intimate arrangement of the various organs of the body. Important, however, as such knowledge is to the full appreciation of all diseased structure and function, its value becomes doubly manifest with reference to the disease now being considered ; for there is probably no affection of the body, the symptoms and physical signs of which may be so easily explained, as may those of pulmonary emphysema, when once we are well acquainted with the structural changes and modiiications by which the disease is accom panied.

Strongly impressed with the force of Lebert's remark, that it is " essential to describe in a rigorously exact manner everything which relates to the affection," and therefore to detail minutely the progressive changes which take place from the earliest periods of the disease, to the time of its full development, it becomes necessary for me to describe briefly the arrangement and structure of the ultimate pulmonary tissue, in order that the changes above alluded to, of which it is the seat, may be the more readily understood.

The bronchial tubes of the lungs, after several divisions and sub-divisions, which, for the most part, are of a dichotomous nature, terminate in a dilatation, into which open a number of cavities, which constitute the ultimate expressions of the air-tubes. These cavities, to which various names have been given, I have elsewhere* called air-sacs, as being, in my oj)inion, more appropriate to their shape and arrangement than any term previously used ; and the series of air-sacs connected with the extremity of each bronchial twig, with its system of blood-vessels, &c., I have called a lohulette.

Each lobe of a lung is composed of a number of lobules, the outlines of which can be seen on the surface of the lung. A lohde is made up of a series of lobulettes, and thus the description of a single lobulette will suffice for that of the entire lobule.

Each lobulette consists of a collection of air-sacs, which vary in number from six to twelve. The air-sacs are somewhat elongated cavities, communicating with the dilated extremity of a bronchial tube by a circular opening, which is usually smaller than the sac itself, and has sometimes the appearance of a circular hole in a diaphragm. When this is the case, the sac dilates suddenly beyond the opening. The sacs of the lobulette are placed side by side, and are separated from each other by thin membranous walls.

* " The Anatomy of the liuuiai: filing," page IIJ5.

EMPHYSEMA OF THE LUNGS.

Their shape, when properly inflated, or when distended by some material which has set in them, as gelatine, or a mixture of wax and turpentine, is polygonal. They approach the circular in form ; but, in consequence of their mutual pressure, the parietes become somewhat flattened. The sacs increase slightly in size as they pass from the bronchial tube to their fundus, the latter being usually the broadest part of the sacs ; but they often have an almost uniform diameter throughout. All the sacs pass from the extremity of the bronchial tube towards the circumference of the lobule of which the lobulette forms a part ; they consequently radiate from the tip of the bronchial twig. The sacs connected with one lobulette do not communicate with those of another lobulette. As the sacs pass towards the boundary of the lobulette, they often bifurcate ; and here and there circular orifices exist, leading to smaller air-sacs. If we trace the air-sacs from their fundus, we may say that, passing from the periphery of the lobulette, and diminishing somewhat in size, they all terminate in the dilated extremity of the bronchial tube ; as they thus proceed, they often join, two or three together, and these terminate in a single mouth. The tube which results from the union of two or more sacs is smaller in capacity than the sacs taken together, but greater than either of them individually. The dilated extremity of the bronchial tube, above alluded to, constitutes the point de reunion of all the air-sacs, and may be considered as the common centre of the lobulette. The air-sacs of the

MORBID ANATOMY.

r adult human lung vary in diameter from l-46th to l-85tli of an inch. (For illustrations of this paragraph, see Plate I., figs. 1 and 2.)

The walls of which the air-sacs are composed are exceedingly thin, and much sacculated; i.e., they have in them a number of small, shallow, cup-like depressions, separated from each other by portions of membrane, which are more or less raised, and project into the interior of the sacs. The bottom of an air-sac presents the same appearance as its lateral walls ; and the cup-like depressions, or alveoli, are there very numerous. The number of these alveoli varies very much ; I have counted as many as ten at the fundus of an air-sac in a cat's lung ; in the human being I have counted five and six, but the number is not usually quite so great. I have found the entire number in each air-sac varying from eight to twenty. (See Plate II., figs. 3 and 4.)

The air-sacs rest, externally, by their fundus, on the pleura ; but within the substance of the lung they in part rest on, and are supported by, the bronchial tubes and blood-vessels.

The air-sacs are separated from each other by thin walls ; the membrane composing which, in a lung inflated and dried, is very transparent. The projections of this membrane in the shape of thin processes, having a sharp margin, constitute the septa between the alveoli; and wherever an opening exists, leading into a smaller sac, this membrane projects in a similar way, and forms a circular orifice, which is much smaller than the cavity to which it leads : the

EMPHYSEMA OF THE LUNGS.

sac, in fact, dilates abruptly on the distal side of the opening. It is in the membrane composing these walls, and in the septa of the alveoli, that the capillaries of the pulmonary artery are spread out.

Each lobulette is separated from those by which it is surrounded by walls, which appear to resemble in every way the walls of the air-sacs ; and in an adult inflated and dried lung, careful observation is necessary to make out the partitions. That perfect septa do exist, is proved by laying open, in a recent lung, a bronchial tube, to its ultimate division; when, by placing a fine blowpipe in it, and blowing down it, a single lobulette is alone inflated.

As I have before mentioned, a number of the lobulettes constitutes a lobule. These lobules are of various sizes ; they are each surrounded by a membranous wall, which is dense and strong, allowing of no communication between, the blood-vessels passing to adjoining lobules. The lobules are connected together by a small quantity of areolar tissue, in which the branches of the pulmonary veins take their course.

The walls of the air- sacs and alveoli are formed of yellow elastic fibrous tissue, a basement membrane, and an epithelium, together with the capillary vessels constituting the pulmonary plexus. The fibres of the elastic tissue are arranged in bundles, and singly. They are found surrounding the mouths of the air-sacs, running through their walls in various directions, and encircling the alveoli. The fibres traversing

M0BB7D ANATOMY.

the walls are placed at some distance from each other, so that spaces are left between them where the blood-vessels are uncovered, except by the basement membrane and epithelium. At the circumference of the alveoli, and at the margins of the sacs, the fibres are often gathered into bundles of considerable size.

It is to this tissue that the elasticity of the air-sacs, and of the whole lung, is due ; and the changes which take place in it, in the disease under consideration, constitute one of the most important features of the affection.

The basement membrane is thin, homogeneous, and transparent. It is a prolongation of that lining the bronchial tubes ; but it becomes finer and more delicate as it passes from the latter vessels into the air-sacs. It is covered by an epithelium, consisting of small flattened nucleated cells.

The capillaries of the pulmonary arteries, which form the pulmonary plexus, ramify in the membrane described above as forming the walls of the air-sacs and the septa of the alveoli. The plexus consists of a single layer of vessels placed between two layers of basement membrane. As the respiratory changes take place in the air-sacs, it is obviously of the greatest importance that the integrity of these latter should remain unimpaired, for any loss of structure they may undergo diminishes the amount of aerating surface over which the blood has to pass. The bearings of these points on the disease under consideration will be dwelt on hereafter.

Having premised these observations on the arrange-

EMPHYSEMA OP THE LUNGS.

ment and structure of the healthy lung-tissue, I pass on to examine the changes it undergoes in the progress of emphysema.

PULMONAEY EMPHYSEMA

is of two kinds : —

I. Vestculae Emphysema.

II. Interlobular Emphysema.

The first is by far the most frequent and most important affection. I have rarely seen the second, except in advanced cases of the first kind.

I. Pulmonary Vesicular Emphysema exists in three forms, which, although they may differ as to their pathological causes, do not differ anatomically except as to the extent to which they involve the lung. We have, firstly, that which is the most partial, and confined to a few air- sacs, or to a single lobulette ; secondly, that in which the whole of a lobule is affected ; and thirdly, that in which the whole of one lobe of a lung, or, more frequently, the whole of the lung itself, is involved in the disease.

1. The first form of the disease, or partial lobular emphysema, is not often seen as an independent affection ; but in lungs in which the second form exists, we occasionally meet with small jDatches of dilated air-sacs, especially along the margins of the lobes — patches which clearly only involve a few air- sacs, or, at most, a single lobulette. These portions resemble enlarged vesicles; and, as pointed out by M. Lombard, of Geneva, many years ago, have very much

MOEBID ANATOMY.

the appearance of the vesicles of pemphigus. They push outwards the pleura, so as to raise it above the level of the surrounding lung-tissue. They are not simple elevations of the pleura, as may be distinctly seen in injected preparations, when the blood-vessels belonging to the air-sacs may be seen ramifying beneath the pleura. Sometimes these partial emphysematous patches are seen extending for some distance along the margin of the base of the lung, and they have then an appearance very like that of a row of beads.

2. The second form, or lobular emphysema, is that most frequently met with; in fact, in the majority of post mortem examinations I have seen, since my attention has been directed to this subject, I have found this form of emphysema more or less prevailing. It involves one or more lobules in different parts of the lung, and is more especially found along the margin of the base, at the anterior border, and apex of the organ. This is the kind of emphysema so frequently met with in cases of phthisis ; I have also seen it in cases of pneumonia where the lung has become consolidated ; and in one instance of this latter kind the emphysema had all the appearances of having been recently produced.

In this form of emphysema it is easy to trace the different divisions of the lung ; the boundary wall of the lobules has not given way, and there is no interlobular emphysema, except in some cases, and to a partial extent. Again, it is by no means essential that all the air-sacs in an affected lobule shall be

EMPHYSEMA OF THE LUNGS.

equally dilated ; the most superficial ones, those especially beneath the pleura, suffer most. At the same time, it must be remarked that this unequal dilatation is sometimes more apparent than real, resulting from the mode of preparation to which the tissue has been subjected, viz., inflation and desiccation. During the process of drying, the air-sacs farthest from the surface collapse most; and thus they have the appearance of being smaller than those which are more superficial, without any real difference having originally existed between the two sets.^'^

The emphysematous lobules are seen on the surface of the lung, protruding beyond the level of the surrounding tissue ; and along the margins of the lobes they often form projections of considerable size, in some instances becoming developed into the so-called " appendages."

3. The third form of pulmonary vesicular eraphy-

* Some anatomists have taught that the "vesicles" of the luugs are larger towards the surface than in the interior of the lungs. This statement seems to me altogether devoid of proof. It is quite true that, in a lung which has heen inflated and dried, the "vesicles" which are situated at the surface, beneath the pleura, appear larger than those which are situated at a distance from it, and from the observation of this fact in all probability the statement has heen made; but it must be borne in mind that this is the result of the collapse of the lung which takes place during desiccation. When a lung is inflated, and slowly dried, the surface is that which dries most quickly ; and the air-sacs and alveoli there situated, being subjected to but little pressure, do not collapse to any very great extent, and thus they maintain a size approaching that they originally had; but with the interior of the lung the case is altogether different; tlie shrinking which necessarily takes place gives rise to considerable pressure on the air-sacs, and collapse of tbem results, producing an appearance of small " vesicles," from the

MOEBID ANATOMY.

sema, or lobar emphysema, is by far the most important. As far as my observations go, it more frequently attacks both lungs than one, and as well the lower as the upper lobes. It constitutes a most formidable affection, and often destroys life at an early period. The cases in which I have had an opportunity of seeing the disease after death, have been those of persons of adult age. Its features are very characteristic, and it is easily recognised during life. It consists of an emphysema of the whole pulmonary tissue of a lobe, or lung. The lung-substance has a peculiar doughy feel, pits on pressure, is wanting in healthy crepitation, and has a colour very closely resembling that of a calf's lung. The whole organ is increased in bulk. No collapse of the lung- tissue takes place when the walls of the chest are removed, in making a post mortem examination ; on the contrary, the lung often bulges forwards, as if its cavity were too small for it.

process which is adopted, and not from any structural arrangement. From the examination of the human lung under various modes of preparation, and of the lungs of other animals, I have been led to the conclusion that there is no real difference of size between the superficial and deep air-sacs and alveoli of the lungs, nor yet between these structures in different parts of the organ ; nor is it easy to see on what principle such a condition would be probable, or on what theory it could be expected.

These observations, with reference to the healthy lung, are equally applicable to the emphysematous organ ; and the facts alluded to should be borne in mind, when we wish to make a comparison between the effects produced by the disease on the superficial and on the deep-seated air-sacG. It is, I think, highly probable that the circumstances I have stated have been overlooked by authors who have written on emphysema, and who have dwelt on the greater liability to distension of the superficial, as compared with the more deep-seated, lung-tissue.

It is also seen to overlap the heart, unless adhesions have occurred which prevent this taking place. The surface of the lung is not unfrequently marked by the impressions of the ribs. If a lung presenting this form of the disease be carefully removed from the chest, and inflated through its bronchus, it will be found that it may be distended to a very large size, without apparently any rupture taking place from the inflation. When the inflation is stopped, the air is expelled from the lung very slowly, and the collapse of the tissue is often very incomplete. The lung presents, when inflated, for the most part, a perfectly smooth and level surface, except in those cases where collapsed portions exist ; or where portions of lung extremely emphysematous form projections or appendages. Often the outlines of the lobules cannot be distinctly seen, in consequence of the rupture of their boundary walls having given rise to the production of interlobular emphysema. When this is the case, the air may be pressed laterally from one lobule to another.