On Diseases Of The Chest

Part II. DISEASES OF THE ‘HEART, AND THORACIC ANEURISM

BY

A. T. H. WATERS, M.D.,

FELLOW OF THE ROYAL COLLEGE OF PHYSICIANS OF LONDON; PHYSICIAN TO THE NORTHERN HOSPITAL,

AND LECTURER ON PHYSIOLOGY AT THE ROYAL INFIRMARY SCHOOL OF MEDICINE, LIVERPOOL.

L 0,$jP 0 N

JOHN CHURCHILL & SONS>;3pW'BURLINGTON STREET.

LIVERPOOL:

1868 ,

Bought in 1915 for the State, lAbrarg,

LIVERPOOL:

Preface

It has been my object, in the following pages, to

depict disease as I have found it at the b.edside,

and to illustrate the application of therapeutics

to thoracic affections by details of cases. • The

work is in nowise a systematic treatise on Diseases

of the Chest, but a series of contributions — chiefly

in the form of lectures — to the clinical history,

pathology, and treatment of some of its more *

important affections. My views on some points in the pathology of the lungs will be found to differ from those of many authors. On this, I will merely remark that the opinions which I have expressed have not been arrived at without careful and prolonged examination of both the healthy and morbid lung-tissue.

Hope Street, Liverpool, 1 March , 1868.

CHAPTER I. Observations on the Anatomy of the Lungs . 1

CHAPTER H.

Pneumonia: its Morbid Anatomy and Pathology. 20

chapter; hi.

Pneumonia: its First Morbid Condition and Earliest Physical

Signs — Cause of the Crepitating Rale, etc. 36

CHAPTER IV.

Pneumonia — Treatment . ... 45

CHAPTER V.

Pneumonia — Treatment — Use of Stimulants — Cases. 53

CHAPTER VI.

Pneumonia complicated with Delirium — Cases — Treatment ... 66

CHAPTER VII.

Pneumonia occurring during Rheumatic Fever . 77

*

VI

CONTENTS.

CHAPTER VIII.

Pneumonia — Treatment — Abstract of Cases — Pneumonia of

Children — Pneumonia of the Aged — Table . 85

CHAPTER IX.

Emphysema of the Lungs: its Morbid Anatomy. 106

CHAPTER X.

Emphysema of the Lungs : its Pathology. 110

CHAPTER XI.

Emphysema of the Lungs: its Determining Causes and Me¬ chanism .1B0

CHAPTER XH.

Emphysema of the Lungs : its Symptoms and Physical Signs ... 145

CHAPTER XHI.

Emphysema of the Lungs — The Sequel® of Emphysema, and

the Diseases associated -with it... *. 157

CHAPTER XIV.

Emphysema of the Lungs — Treatment of Emphysema, and of

the Diseases connected with it. 171

CHAPTER XV.

(Edema of the Lungs — Pulmonary Apoplexy . 195

CHAPTER XVI.

Gangrene of the Lung — Phthisis with Fetid Expectoration —

Bronchitis with Fetid Expectoration. 204

CHAPTER XVII.

CONTENTS.

Vll

CHAPTER pPIg Phthisis: its Nature and Treatment

CHAPTER

Che;

IS

XIX.

Researches on Asphyxia (Apnoea) — with Observations on the Effects produced by the Hot Bath in Asphyxiated Animals, and its Use in the Treatment of Suspended Animation ... 257

CHAPTER XX.

Observations on the Rhythmical Action of the Heart, and its

duration in Apnoea .273

CHAPTER XXI.

The Apnoea of Still-born Children.280

CHAPTER VII. On the Use of Alcoholic Stimulants

PAGE

•til

PLATES.

PLATE

I., Fig. 1. — Air-Sacs of Healthy Lung (Adult Human). Fig. 2 .— Do. Do. Do. (Infant).

PLATE II, Fig. 3.— Slice of Cat’s Lung.

Fig. I. — Do. Human Lung.

PLATE III., Fig. 5. — Epithelial Cells of Air-Sacs (Human).

Fig. G. — Do. Air-Passages of Pigeon.

Fig, 7. — Pulmonary Plexus (Human).

PLATE IV., Fig. 8.— Air-sacs filled with Pneumonic Exudation.

Fig. 9. — Terminal Bronchial Tube, with Air-Sacs. Fig. 10 . — A single Air-Sac.

PLATE V., Fig. 11. — Air-Sacs of Emphysematous Lung.

Fig. 12.— Do. Healthy Lung.

PLATE VI., Fig. 13. — Slice of Healthy Lung-Tissue.

Fig. 14.— Do. Emph 3 T sematous Lung-Tissue.

PLATE VII., Fig. 15. — Air-Sacs of Emphysematous Lung.

PLATE VIII., Fig. 1(5.~ Do. Do. Do.

PLATE IX., Fig. 17.— Slice of highly Emphysematous Lung-Tissue.

Fig. 1.

Fig. 1 is a drawing of a termiual bronchial tube, with a group of air-sacs, or lobulette, connected with it, divided transversely (human). a , the terminal bronchial tube ; h, the dilated extremity of the terminal bronchial tube; a c c, individual air-sacs. At <7, a bristle is seen passed into an air-sac ; one 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 the 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. b, terminal bronchial tube ; c r o, air-sacs; tl d, openings leading to air-sacs beneath those exposed. This diagram was taken from the lung of an infant under one year of age.

Fig. 3.

Fig. 3 represents a very thin slice of a cal's lung (injected, inflated, and dried), from the surface of the lung. The eye is looking upon the rut surface. Tin* depressions, a a, are the bottoms of the air-sacs, resting on the pleura. The light coloured lines that surround them are their walls, and tin; small depressions seen within the walls, bb. marked oil' 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 con¬ sidered as fairly representing the appearance presented.

Fig. 4.

Fig. 4 is a drawing of a similar slice to that of Fig. 3, taken from a human lung, a a n are the air-sacs, b b the alveoli. The lighter por¬ tions represent the walls of the air-sacs and the alveoli.

Eig. r> shews the aiipearanee of the epithelial cells lining the airaes, highly magnified, and treated with acetic acid. Some of the i nitre cells were drawn with the aid of the camera lucida, their out¬ line being traced as thrown down on the paper.

Fig. (). Epithelial cells lining the air-passages of the pigeon, highly tmgnilied. Drawn with the aid of the camera lucida

Fig. 7.

Fig. 7 shews the arrangement of the pulmonary plexus in the air-sacs of the lung, a, branch of pulmonary artery.

PLATE IV.

Em. H.

Fig. 8 represents the air-sacs distended with exudation. (Pneu¬ monia— stage of hepatization.)

Fig. 9 represents a terminal bronchial tube with a group of air-sacs ; a, terminal bronchial tube ; b, dilated extremity of the terminal bronchial tube forming the point de reunion of the air-sacs; e. r. air-sacs ; d d, mouths of air-sacs.

Fig. 10 represents a single air-sac.

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 ot fht* air-sacs, more or less obliteration of the alveoli, and slight perforation. The black spots represent the perforations. Tin* air-saes in the. pioeo oi lung examined varied in diameter from L-20th to 1-dOth of an inch — being more than double their ordinary size in health.

Air-sacs from the same lung as Tig. 11, but not emphysematous. The alveoli are shewn with their septa well marked. The diameter of the sacs in the part examined varied from 1-4,ith to l-?0th of an inch. Figs. 11 and 12 were both taken by means of the camera lucicla, and the same magnifying power was used in both. They therefore shew the relative size of healthy and emphysematous air-sacs.

Air-sacs of emphysematous lung, as seen through dissecting micro¬ scope. The bristles are passed through the sacs. The upper walls of two sacs and tilt 1 lower wall of one sac, are seen with their perforations.

I'LATH VII!.

Taken from a portion of lung very emphysematous. It shows the appearance of the air-sacs in a dilated condition, with their partitions much nipt un'd, and full of large perforations. (Drawn by means of the camera lueida.) The black spots shew the perforations. The cavities — tin* distended and broken-down air-sacs — in the piece of lung from which this was taken had a diameter of l-lf>tli. l-20tli, and 1 -2?tli of an inch.

PLATE IX,

Chapter I. Observations On The Anatomy Of The Ltjnos

The bronchial tubes of the lungs, after several divisions and sub-divisions, which are, for the most part, dichotomous, terminate in a dilatation, into which opens 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 opinion, 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, &c., I have called a lobulette .

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 lobule 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, varying in number from six to twelve. The air-sacs are somewhat elongated cavities, communicating with the dilated extremity

* “ The Anatomy of the Human Lung,” page 135,

B

& tk

DISEASES OF THE LUNGS.

of a bronchial tube by a circular opening, which is usually smaller than the sac itself, and has sometimes the appear¬ ance of a circular hole in a diaphragm, or as if it had been punched out of a membrane stretched across the entrance to the sac. 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. 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 mutual pressure, the parietes become some¬ what 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 circum¬ ference 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 com¬ municate 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

ANATOMY OF THE LUNGS.

lobulette. The air-sacs of the adult human lung vary in diameter from l-45th to l-85th of an inch. (For illustra¬ tions of this paragraph, see Plate I., figs. 1 and 2.)

The walls of which the air-sacs are composed are exceed¬ ingly 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 anterior 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 generally some¬ what less. 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, con¬ stitute the septa between the alveoli; and wherever an open¬ ing 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 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.

As I have before remarked, the number of air-sacs belong¬ ing to a lobulette varies: I have counted as many as six

DISEASES OF THE LUNGS.

communicating with a bronchial tube incised horizontally, so that probably only half the sacs were left; this, however, is a larger number than is usually found; from six to eight or ten is the more common number.

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 par¬ titions. 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.

The separation of the lobulettes is further distinctly per¬ ceptible in the recent lungs of infants, in which the line of demarcation between the lobulettes is often plainly seen, on the surface.

The observation of the foetal lung, however, affords most satisfactory evidence of the separation of the lobulettes, and tends to confirm the views here taken of the arrangement of the ultimate air-tubes.

The recent lung of a full-grown foetus presents on its surface no appearance of air-sacs, vesicles, or cells; but if it be inflated, it will present different appearances, accord¬ ing as the inflation has been partial or entire. In a portion of lung only partially inflated, a number of tubes will be seen terminating beneath the pleura in csecal extremities, their light colour contrasting strongly with the surrounding dark-coloured tissue. The exact arrangement of these tubes may be sometimes observed. They will be found to exist in groups or clusters, and to pass from the csecal ends to a point, in which they terminate, and where they all appear to join; or, to describe them in the inverse direc¬ tion, they pass from a point at some distance from the surface, and radiate towards the pleura. The tubes are

ANATOMY OF THE LUNGS.

b seen to liave numerous constrictions ami bulging*; they terminate in extremities rounded, or nearly so. In a pre¬ paration of this kind it is often easy to sec the bronchial tube for a short distance before it terminates; and not only is the terminal group of air-sacs (lobulettc) visible, but two or more of the previous ones arising laterally from the bronchial tube may be also seen. The uninflated lung-substance lying between the distended air-sacs is distinctly seen when there has been only slight inflation; and the isolated condition of each group of sacs is very apparent; the sacs passing from different points radiate in different directions. In a lung which has been fully inflated, the grouped appearance is lost, and the ordinary condition of the distended lung is observed.

If, in a foetal lung, we follow 7 out a bronchial tube, we find that the smaller branches of the tube have, connected with them, clusters of little pyriform red-coloured bodies, which look very much like a number of grapes attached to their stalks. In a foetus of six months, I have found it somewhat difficult to separate each individual body, but in a full-grown foetus there is no difficulty in doing so; each little body is attached to a short pedicle. If air be blown down a bronchial tube leading to the exposed bodies, the latter become distended.

The little bodies just described are the ready-formed groups of air-sacs, or lobulettes; the pedicle with which each is connected is the terminal bronchial twig. The lobulette thus formed is surrounded by its sheath, and no communication exists between it and adjoining ones.

That the appearances I have described in the artificially inflated foetal lung are not the result of any abnormal dis¬ tension, I have been able to prove by observing the same appearances in the lung of a child in which only partial respiration had taken place.

DISEASES OF THE LUNGS.

Different opinions have been exiiressed ns to whether the air-sacs communicate with each other by any orifices except that by which they communicate with the bronchial tube. Adriani states that he has observed such orifices, and spe¬ cially mentions that they are most clearly to be seen in the stag. Dr. Thomas Williams considers that the “intercellular passages ” intercommunicate, and are perforated by secondary passages at every point. Rossignol, Schultz, Mandl, and Milne-Edwards deny the existence of such communications. From observations, made with much care and frequently repeated, I have satisfied myself that the opinion expressed by the latter authors is correct. I have newer found, either in the lungs of man or in those of the dog, cat, pig, sheep, or any other mammal I have examined, any lateral orifices of communication between the sacs of a lobulette.

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 termination of each bronchial tube has a particular and special character. It differs in its anatomical arrange¬ ment from the other portions of the tube, and, no doubt, differs also in function; it constitutes, in fact, a part of the true respiratory system. As this condition of the bronchial tube has important physiological and pathological bearings, I shall refer to it in detail.

Rossignol was the first who pointed out the existence of a structure, at the termination of the bronchial tubes, similar to that which exists in the air-sacs. He says : “ In the bronchial divisions of the two last, and sometimes three last

ANATOMY OF THE LUNGS.

orders, it is plainly seen, when they are opened longitudi¬ nally, that their surface is covered over, or, as it were, honeycombed, by a number of small regular shallow cavities, placed side by side, and separated by thin perfect walls of the same height, which project into the interior of the bron¬ chial tube.”

The existence of these bronchial alveoli has been noticed by subsequent observers. They may be easily seen in a lung injected, inflated, and dried, and sometimes even in one which has been simply soaked in spirit for a few days. They resemble the alveoli of the air-sacs; they consist of little cup-like cavities, resting upon the bronchial tube, and opening into its cavity; they arc surrounded by walls, and their shape is more or loss oval, or circular, quadrangular, or polygonal. In a preparation in which the pulmonary artery has been injected, branches arc seen to pass from that vessel to these alveoli, before it reaches the air-sacs.

These alveoli are best seen in the lungs of some of the lower animals. In the cat they are especially distinct, and very easily recognised; in this animal they are found in the last ramifications of the air-tubes and their dilated extremity. In man, however, I have never seen them except at the extremity of the tube, and in many lungs I have examined,

I have found no appearance of them at all. This is to be explained by the fact that these alveoli diminish in number with advancing age. It would seem that as the lungs become more distended, these depressions or cavities become more and more obliterated. In the infant I have found the alveoli in the last bronchial tubes and their dilated extremities, but I have not found them in the penultimate and earlier branches, and even in the last branches they do not always exist previous to the dilatation. "When the alveoli are found in the tube previous to the dilatation, they do not generally commence abruptly, hut, being thinly scattered at first, their

DISEASES OF THE LUNGS.

number gradually increases. As far as my observations go they are very rarely to be found in the adult, and never in the aged, except in the terminal dilatation.

It will be seen that my observations, as to the tubes in which these alveoli are found, do not quite accord with those of Rossignol, who places them in the two or three last divi¬ sions of the tubes, whereas I have never been able to find them except in the last. It seems to me probable that Rossignol has drawn his conclusions from observations on the lungs of the lower animals, in some of which, as, for instance, the cat, they exist to a greater extent than in man.

The walls of the air-sacs and alveoli are formed of yellow elastic fibrous tissue, a basement membrane, and an epithe¬ lium, together with the capillary vessels constituting the pulmonary plexus. The fibres of the elastic tissue are arranged in bundles, and singly. They are found sur¬ rounding the mouths of the air-sacs, running through their walls in various directions, and encircling the alveoli. Tho fibres traversing the walls are placed at some distance from each other, so that spaces are left between them where tho blood-vessels are uncovered, except by the basement mem¬ brane 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 tho air-sacs, and of the whole lung, is due; and the changes which take place in it, in one of the diseases to be hereafter con¬ sidered, constitute a most important feature of the affection.

The basement membrane is thin, homogeneous, and trans¬ parent. 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.

Some difference of opinion exists as to the presence of an epithelium on the walls of the air-sacs. From

ANATOMY OF THE LUNGS.

careful and repeated examination of a very considerable number of specimens of the lungs of man, and of various mammals, I have satisfied myself of the existence of such an epithelium. No doubt whatever can be entertained, that the ciliated columnar epithelium, so characteristic of the bronchial mucous membrane, ceases at the commence¬ ment of the alveoli—the true respiratory portion of the lungs; for in no instance, in which proper precautions have been taken to avoid errors, have I seen an epithelium of such a character present in the air-sacs. It seems to me altogether unnecessary to attempt to prove, from analogy, that an epithelium ought to be absent or present in the true pul¬ monary system, for if the fact be capable of demonstration, no theoretical argument against it can ever avail, and none in proof of it is required.

If a piece of the fresh lung of any mammal bo taken, the pleura carefully stripped from it, and a small portion of the pulmonary tissue be removed and washed, and then placed under the microscope, an appearance will be observed not very unlike that which is presented by the free surface of a serous membrane. The portion of tissue examined will be found covered with a number of small flattened bodies, of various sizes and shapes, many of them approaching the circular, but most of them being polygonal; beneath these bodies, in different parts, will be seen bands of yellow elastic fibres and capillary blood-vessels. The flattened bodies are tolerably distinct, but the outline of many of them is faint; nuclei are apparent in a large number of them. (See Plate HE., figs. 5 and 6.)

Pound the sides of the piece of tissue under examination a number of detached bodies, and also small granules, will be seen, resembling those just described. If now acetic acid be added, the outline of these bodies becomes more distinct, and the nuclei more apparent. These bodies have all the

DISEASES OF THE LUNGS.

characteristics and appearances of epithelial cells, and such they seem to me to be. They have not quite the same appearance as those of a serous membrane ; they are smaller, and more rounded in shape, and less distinct in outline, but in the possession of nuclei (which are \isiblo in all after the addition of acetic acid) and granular matter, they resemble the ordinary pavement epithelia.

The cells form a distinct and complete coating to the walls of the air-sacs and alveoli, and they rest immediately upon the basement membrane. My measurements have given from 5 oV o to 3 cfe o of an inch as the diameter of these cells. In the cat, I have found them varying from Woo to Wo o of an inch; in the sheep, from Woo to 3 Wo of an inch.

Although, as I have previously stated, demonstration is better than analogy, yet, with reference to the existence of any particular structure of the human body, it becomes of the utmost importance to ascertain how the parts which have a similar function to perform in other animals are con¬ stituted; and especially does this apply where investigation can only be carried on by means of the microscope. I have frequently observed a pavement epithelium present in the lungs of reptiles; and the existence of an epithelium in the air-passages of the bird seems to me to be so obvious, as not to leave the slightest doubt of the fact. Under a magnifying power of 360 I have seen the cells perfectly .distinctly. They are very small, and present at first a very faint outline, but, on the addition of acetic acid, their outline comes clearly into view, and their nucleus is ren¬ dered very apparent. On the gills of fishes an epithelium of a similar character is also easily recognised.

In examining these epithelia, a perfectly fresh lung should be used, for they seem soon to become destroyed, or at least to lose their characteristic appearance.

The capillaries of the pulmonary arteries, which form the

ANATOMY OF THE LUNGS.

pulmonary plexus, ramify in the membrane described above as forming the walls of the air-sacs and the septa of the alveoli. 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 pathological bearings of these points will be dwelt on here¬ after.

The Blood-vessels of the Lungs. — The Pulmonary Arteries . — The branches of each pulmonary artery, on entering the lungs, attach themselves to the bronchial tubes and their divisions, and accompany them through¬ out their course as far as their termination. This arrange¬ ment presents no exception in any jmrt; the number of branches of artery is equal to the number of bronchial tubes; but at the termination of those tubes, where the air-sacs commence, a difference of arrangement exists.

Although every bronchial tube has its accompanying artery, yet these are not always given off at the same level as the tubes themselves. The vessels pass from the main trunk at obtuse angles; many of them have to pass partly round the air-tube which is the satellite of their trunk, to reach the tube for which they are destined.

Each branch of a pulmonary artery, as it accompanies a bronchial tube, distributes its branches in like manner with the tube itself, and thus often divides dichotomously; every lobule has its artery entering it, which at its entrance is a little less than the bronchial tube, but as the vessel gives off branches it gradually diminishes in size more rapidly than does the tube, so that at the termination of the latter the artery is not more than one-fifth the size of the tube.

Erom the second and third divisions of the arteries some

DISEASES OP THE LUNGS.

ftmn.H vessels are given off, which do not correspond with any divisions of the air-tubes. These small vessels pass off nearly at right angles, and may he traced, passing to portions of the pulmonary substance, which lie m close contiguity with the arteries.

The branches of the artery are connected with the bionchiai tubes, and with the lung substance, by means of areolar tissue, which is loose and somewhat coarse in the larger vessels, near the root of the lung; but in proportion as the vessels become smaller, so does the connection become more and more intimate, and the tissue of union closer in its character, so that, when the artery reaches its lobule, it is closely applied to the parts with which it is in contact.

When the artery reaches the termination of the bronchial tube it gives off a number of branches, which are distri¬ buted to the air-sacs; before doing so, however, branches are derived from it which pass to the alveoli situated at the termination of the tube; these latter branches terminate in plexuses which are formed in the alveoli, and are arranged in a similar manner to those which exist in the air-sacs. The branches destined for the air-sacs take their course in the walls which separate the sacs from each other; they do not pass in any very regular or definite manner, but run in different parts of the sacs, and in different directions, along their entire length. Many of them may be observed passing straight from the commencement of the sacs to their fundus, and this course is more or less observed by all. .In whatever way the arterioles pass, they gradually diminish in size as they proceed to the fundus of the sacs ? and this diminution results from the giving off of a number of lateral branches from both sides of the vessel; these branches pass off at right or obtuse angles, and run in the walls of the sacs, they pass round the circumference of the sacs, and unite with branches coming from other arterioles,