clouds in the sky. Some days after, the newspapers were filled with the account of ravages caused by storms in Baden, Wurtemberg, and Bavaria: even in the country of Vaud, the lightning struck several houses. If the newspapers had also mentioned the storms that had occurred in this neighbourhood, without causing mischief, we might have seen that there were some even closer still." 375.

Among the electrical phenomena of the atmosphere our author enumerates hail the formation of which meteor has long been, and still remains, a subject of difference of opinion. How, for instance, are we to explain the circumstance that hail-storms are infinitely more common during the day than during the night? and that, in the majority of instances, they are observed in warm weather, at, or soon after, noon, about the period of the greatest diurnal heat? Then again, how comes it that certain places are ravaged by hail-storms almost every year, whilst adjacent localities are almost entirely spared? These, and many other points connected with the history of this atmospheric phenomenon, are far from being well understood.

Aristotle and Lucretius have said that a loud noise may often be heard when a cloud, charged with hail, approaches the zenith. This observation has been confirmed by several modern writers; while others have either questioned, or wholly denied its accuracy. As we have already mentioned, hail-showers are frequently very limited in their extent: at a short distance from where the hail fell, perhaps not even a puff of wind has been felt. The following is a curious example of this circumstance :

"The storm commenced in the morning in the south of France, and in a few hours reached Holland. The places destroyed by the hail formed two parallel lines from S.W. to N.E.; one was 70 and the other 80 myriameters long. The mean width of the west line was 16, and that of the east line 8 kilometres. The space comprised between the two lines, the width of which was 2 myriametres, was spared; there merely fell a heavy rain. It also rained much on the east and the west of the two lines. The storm was preceded by an obscuration of the light of day; it travelled about 66 kilometres per hour, and its velocity was the same in both the zones. In the west zone the hail fell at La Rochelle, after a storm that had lasted all the night; at 17h 30m, in Touraine, near Loches; at 18 30, near Chartres; at 19 30m, at Rainbouillet; at 20h, at Pontoise; at 20h 30m, at Clermont, in Beauvoisis; at 21, at Douai; at 23h at Courtrai; at 0h 30m, and at Flessingue, about 1h 30m. In the west zone, the storm reached Artenay, near Orleans, at 19h 30m; Andouville, in La Beauce, about 20h; the Faubourg St. Antoine, Paris, 20h 30m; Crespy, in Valois, about 21h 30m; CateauCambresis, 23; Utrecht, 2h 30m. At each place the hail only fell for seven or eight minutes, but with so much violence, that all the harvests were cut to pieces. Of all the great hail-storms, there is not one of which we have such exact information, and yet it is still insufficient; thus the direction of the wind, and that of the clouds before and after the storms, and on the two sides of the space where the hail fell, have not been pointed out." 384.

According to Dr. Kraemtz, the production of hail-which, it is to be observed, is almost invariably preceded by oscillations in the barometric state of the atmosphere-is attributable to the conflict of two opposing currents of wind from the north and south, (the latter charged with moisture)-the greatest fall taking place where the shock is the most violent. After a hail storm, the weather-which usually has been hot for some time before-often remains unsettled for weeks; very frequently it is followed with cold. The rise of the barometer proves that the north wind

generally obtains the predominence; and the more so, as, in melting, the hail absorbs a very notable quantity of heat.

"The conflict of opposite winds," our author remarks, "also explains certain peculiarities of storms, accompanied by hail. Every thing that tends to put the air in motion favours the formation of hail. This is why it is more common in the mountains, where the rapidity of the atmospheric current increases in the valleys. If the march of storms were known by observations embracing a series of several years, by comparing local peculiarities, we might discover why certain countries are frequently ravaged by hail, whilst others are almost entirely spared. Narrow valleys, surrounded by high mountains, as the Valais and the vale of Aoste, are rarely visited by hail: these valleys are so warm, that the hail-stones melt before reaching the ground. Moreover, the high mountains that hang over them prevent the conflict of opposite winds, or limit it to the high regions of the atmosphere, which prevents the hail-stones acquiring any considerable volume. But, at the mouth of valleys, in the plain, storms, accompanied with hail, are the more violent (principally on the south side of the Alps), as the south winds are arrested by the mountains, while the north winds, when they have traversed them, rush impetuously to the plain." 391.

With the following quotation on the curious subject of Terrestrial Magnetism, we close our notice of this interesting volume :

"Every where, on the surface and in the interior of the globe, the magnetic needle takes a determinate position; this position varies in each country of the earth as we advance, proceeding directly to the west, we see that it increases, and attains its maximum in the Atlantic Ocean. From this point, the western declination diminishes; and at the east of the United States, the needle points exactly to the north pole; and consequently the declination is nothing; more westward, the declination becomes east. If we had gone toward the east, the west declination would have diminished; it would be nothing in the east of the Russian empire; and then east, if we had continued our course towards the

east.

"In general, if, under any parallel, we take the circuit of the globe, we shall find a point where the needle is directed toward the north; afterwards the deviation becomes westerly, attains its maximum, and then diminishes, until it is nothing thus the declination varies greatly. If we make our experiments under the equator, and repeat them every five degrees, we shall find that the difference between the maximum eastern and the maximum western declination increases as we approach the poles of the earth. Thus, in Greenland, the west declination is so great that the needle points to the west; and Parry found a point, in the west of Greenland, where the north pole of the needle was turned to the south.

"The dip presents similar differences; in our countries it is northern, that is to say, the north pole is directed downward, and forms an angle of 70° with the plane of the horizon. In proportion as we advance toward the south, the needle approaches the horizontal direction, and, in the neighbourhood of the equator, it is altogether parallel to the horizon: the dip is, therefore, nothing. On passing into the southern hemisphere, we see the south pole of the needle dip, and the more so as we approach the south pole; going toward the north, the contrary would have been observed: thus, in one of the hemispheres, the dip is northern, and, in the other southern. These two hemispheres are separated by a line of dip, upon all points of which the needle is horizontal: this line, which cuts the equator in different points, and rises alternately into each hemisphere, is called the magnetic equator." 548.

MEDICO-CHIRURGICAL TRANSACTIONS, PUBLISHED BY THE ROYAL CHIRURGICAL SOCIETY OF LONDON. Volume

MEDICAL AND

the Twenty-seventh, (the Ninth of the Second Series,) 1844. Continued from page 32.

XVI. ON OBSTRUCTIONS OF THE BRANCHES OF THE PULMONARY ARTERY. By James Paget.

THE obstructions treated of in this paper, are those produced by the coagulation of blood during life in the branches of the pulmonary artery. They are not of rare occurrence, and, the author observes are always important, for they are sometimes the sole or chief cause of death, and must in all cases seriously affect the progress of the diseases with which they are associated. Yet they have hitherto scarcely attracted attention, and in the only paper which he can find expressly treating of them (one by M. C. Baron, in the Archives Générales de Médecine, Paris 1838) there are but four cases related, and these give a very imperfect account of the nature of the disease and of the circumstances in which it occurs.

"From the arrangement of the pulmonary arteries, between which there is no anastomosis, except in their capillaries and smallest branches, it results that whenever the flow of blood through the capillaries of any part of a lung, is prevented, there must also be a stagnation of the blood in all the branches from which those capillaries are derived; and in these circumstances, the blood coagulates in the vessels, and passes through various changes." 163.

Now these conditions are present in several diseases ;-First, in pulmonary apoplexy, especially in that form of it in which the blood collects in a defined and compact dark mass. In all, or in a great majority of these cases, the branches of the pulmonary artery leading to the seat of effusion are blocked up by coagula, which present the distinguishing characters of those formed long previous to death.

Secondly. The capillary circulation is usually obstructed or much hindered in the advanced stages of pneumonia, and the arrested blood coagulates in those branches which correspond to the inflamed and consolidated portions of lung. So far as the author has seen, "the coagula in these cases are not sufficiently large to fill the vessels; circulation enough, therefore, may go on to prevent gangrene; but still, such permanent, though imperfect, obstacles to the passage of blood must materially impede and endanger the recovery of the diseased part, and no doubt the formation of these clots often precedes the complete obliteration of the pulmonary arteries, when, after partial recovery from pneumonia, the diseased portion of the lung has healed and contracted. Sometimes, indeed, coagula thus formed in pneumonia are fatal. They were so in one of the cases mentioned by M. Baron. A patient of M. Louis' was suddenly seized with symptoms of asphyxia during convalescence from pneumonia: he died in five or six hours, and nothing could be found to explain his death, except some soft non-adherent clots, which obstructed the cavity of the pulmonary artery."

Thirdly. When the matter of medullary cancer or of softened scirrhus passes into the blood, and, circulating with it, is stopped in the lungs, the branches of the pulmonary artery may be to a great extent filled by it and by coagulated blood or fibrine mixed with it. Mr. Paget relates a case

which affords a good example of this fact. It was the case of a woman affected with carcinoma of the liver. On examination of the body, it appeared that the cancerous substance had been conveyed with the blood from the liver to the lungs, where, being arrested and obstructing the minute vessels, it had permitted fresh substance with blood to accumulate behind it. Some other cases in which similar appearances were found in the lungs are also mentioned.

Fourthly. The branches of the pulmonary artery are often blocked up by clots formed during life in those who die with great oedema of the lungs. In some of these cases the coagulation is probably consequent, as in pulmonary apoplexy from disease of the left side of the heart, on the obstruction to the passage of the blood through the capillaries. But the author is of opinion, that in general some further condition is necessary, and he gives two cases of coagula occurring with oedema of the lungs, in one of which sufficient evidence of morbid state of the blood is afforded by the signs of its early decomposition after death.

Mr. Paget remarks that, in these four classes of cases, "the coagulation of the blood in the pulmonary arteries may be regarded as a secondary phenomenon; for it usually appears as the consequence, either chiefly or entirely, of the obstruction in the capillaries. Whenever that obstruction is complete, and prevails through the whole of both lungs, death by asphyxia must ensue before the arrested and coagulated blood can undergo any structural changes; and such changes can take place only when the capillary circulation can be carried on in some parts of the lungs, at the same time that in others the blood is stagnant."

The author believes, also, that in some other diseases under the same essential conditions similar coagula are often formed. But there are other classes of cases in which their formation appears to be a primary disease, or in which at least it cannot be regarded as the result of mere obstruction in the capillaries. Of these he has observed three examples. The first is the case of a woman, 29 years of age, who was admitted into St. Bartholomew's Hospital, May 5th, 1843, with symptoms of rheumatism, attended with a good deal of depression of the system, and a rapid pulse and respiration. After a few days the abdomen became distended, and rather painful on pressure; on the next day she complained of great tenderness in the right iliac region; and on this day also (May 9th) the præcordial region was found tender, and on auscultation, a distant bellows sound was heard at the base of the heart accompanying the systole.

"On the 10th, the cheeks and forehead were covered with an erysipelatous blush, and numerous red acuminated papulæ had appeared upon the chest, the urine was very irritating, and smelt offensively, sloughs had begun to form upon the sacrum, and the weakness and depression were increased. On the morning of the 11th, after passing a comfortable night, she was suddenly seized with a sensation of great tightness in the præcordial region, violent palpitation of the heart, and the most urgent dyspnea. The attack lasted for an hour, and then she returned to nearly the same state as she had been in before it; but from this time she sank more rapidly. Upon auscultation, no

respiratory murmur was heard below the right breast, and it was dull on percussion; the habitual dyspnea became greater, the sloughs on the nates and sacrum extended, the abdomen became again tympanitic and tender, especially about the right iliac region, she vomited several times, and died in the afternoon of the 13th." 176.

On examination 40 hours after death, all the blood which appeared in the ordinary course of the dissection was found either fluid or coagulated in soft black masses. The pericardium contained half an ounce of fluid, and there was a few slender adhesions between the trunks of the larger vessels. No particular disease of the heart and principal vessels. A small quantity of fluid in each pleural sac. Lower lobes of both lungs œdematous and gorged with blood. Trachea and bronchi healthy. "Nearly half the branches of the pulmonary artery, from those of the second order, to those of the fifth and sixth (and probably to yet smaller branches,) were blocked up by old coagula of blood. These were cylindrical, soft, and grumous, and in colour were a mixture of pale pink and dirty greyish white, with spots and blotches of deep crimson. They were not more numerous in one lung than in the other, and were irregularly scattered through all parts of each. They did not quite fill the vessels which contained them, but at various parts they adhered closely to the walls. The trunk of the pulmonary artery, and many of the branches which did not contain coagula of the kind just described, contained fluid and softly clot ted black blood." Abdominal and pelvic organs healthy.

In the next case, a woman, 70 years of age, who had suffered for five weeks from a bad cold, was taken into the hospital in a declining state. On the day after her admission, she seemed to improve a little, but next day she sank rapidly, and Dr. Burrows "remarked an extreme hurry of the circulation, with feebleness of the pulse and great prostration of strength, very similar to those observed in the preceding case.' On examination of the body 36 hours after death, there was no other particular disease except a small patch of compact pulmonary apoplexy with some diffused apoplexy around it, at the anterior and lower border of the left lung; and "in each lung, one of the superior, and one of the inferior main branches of the pulmonary artery were blocked up by a large, firm, mottled, clot of blood, which, from itself as a trunk, sent branches into two or more of the next order of branches of the artery. The colours of the clots were black, deep-crimson, rusty, pink, and yellowish, in various irregularly mingled shades; they were moderately firm, of nearly uniform consistence throughout, and capable of being rubbed into a thick grumous substance; they adhered so firmly by parts of their surfaces to the adjacent walls of the vessels, that they could not be smoothly removed. The branches of the largest clots did not extend far into the arteries, but terminated abruptly in the arterial ramifications immediately proceeding from those in which they lay. But beyond their terminations, many smaller branches of the pulmonary arteries in all parts of the lungs contained short, firm, dry, mottled, and adherent clots, variously coloured. None of these was long or much ramified; none was continued through more than two branches; and many of them were not more than half or three quarters of an inch long; some were even shorter, and lay like bits of larger clots upon the walls of the vessels. They had all the same characters as those