three-fourths was hepatized. The bronchi contained a muco-purulent secretion. The hepatization was of a bright red color, mottled in many cases with greenish-yellow, necrotic areas; in others the necrosis was absent. The pneumonia was accompanied in most cases by more or less extensive exudative pleuritis, limited, at least in its severer form, to the covering of the solidified lung tissue. The pericardium, and more rarely the epicardium, was covered with the same exudate. As a rule the lobes of the lungs were glued to each other, to the chest wall, and to the diaphragm. The lesions of the digestive tract involved the stomach and the large intestine. The former was usually hyperemic, bordering on hemorrhage, occasionally with localized sloughs or ulcers. The large intestines were as a rule ulcerated, but the ulceration varied very much. In some animals it was limited to the follicles, in others the necrosis of the mucous membrane was very extensive. Pigmentation and hyperæmia were not uncommon.

The bacteriological examination comprised cultures on gelatine, agar, and in bouillon, from the spleen, liver, and pleural exudate; gelatine and agar roll and plate cultures from different regions of the diseased lung tissue, and the inoculation of rabbits with bits of the same tissue. The results of this laborious examination are somewhat different from those obtained from former outbreaks, and they indicate how important it becomes in these inquiries to know something of the previous history of the infected herd.

An examination of the table shows that in spite of the careful search no hog-cholera bacilli could be found in Nos. 1, 2, 5, 7, 8, and 12, while on the other hand no swine-plague bacteria could be found in Nos. 4, 6, and 13. The rest-Nos. 3, 9, 10, and 11-contained both hog-cholera and swine-plague bacteria. In general, the lesions cor responded with the bacteriological facts. This was particularly so with the first four cases examined. In Nos. 1 and 2 the ulceration of the large intestine was slight, apparently follicular, while the lung disease was very severe. In Nos. 3 and 4 the reverse was true; the intestinal ulcers were very large and numerous, the lung disease moderate and without pleuritis. In Nos. 1 and 2 no hog-cholera bacilli could be found, although special attention was paid to this point. In No. 4 no swine-plague germs could be found; in No. 3 they were only detected by rabbit inoculation with bits of lung tissue. In cultures from the other organs hog-cholera germs were present exclusively. In the other cases a similar parallelism between the lesions and the germs found was present, but not so well marked as

37

If we had limited our investigations to Nos. 1 in the first four cases. and 2 we should have no doubt considered the outbreak as swine plague. If we had only examined No. 4 we should have pronounced the disease hog cholera, whereas, in fact, the herd was affected with both diseases.

When the

If we should attempt an explanation, by using statements which can not be clearly demonstrated as facts, we might come to the following conclusions: The pigs, which came from two or three different sources, came infected with two different diseases. This view will be borne out by the earliest four cases actually examined. animals were thrown together secondary infection took place, those having swine plague becoming infected with hog cholera, and those having hog cholera with swine plague (see Nos. 9, 10, 11). As regards the intestinal lesions in those animals in which, after very diligent search, no hog-cholera bacilli could be found, we do not venture an opinion, because the hog-cholera bacilli may have been limited in their distribution to the digestive tract, which was not examined directly. What may be maintained, however, is that in these cases the internal organs were flooded with swine-plague germs; the diseased lungs, also flooded with swineplague germs, after very careful examination proved to be free from hog-cholera germs. When we take into consideration the fact that when hog-cholera germs are at all present in the diseased animal they generally appear in all organs, and that they are far more easily detected there than are the swine-plague germs-the latter generally failing to grow on gelatine-we may safely assume that in those cases in which hog-cholera germs were not detected they were either wholly absent, or, when present, exercised a very minor influence on the course of the disease, and that the swine-plague or infectious pneumonia was the primary disease and the cause of death.

In view of the skepticism which prevails to some extent as to the existence of a disease independent of log cholera, the following inoculations, which clearly demonstrate the pathogenic effect of the swine-plague germ, are briefly reported:

Four pigs were inoculated with a turbid suspension of swine plague germs, grown on agar.

No. 272 received 2 cubic centimeters subcutaneously; killed after three weeks. No effect.

Dia

No. 273 received one-half cubic centimeter through the right chest-wall into the lungs. Sick for a week, breathing with difficulty. Seems to have recovered after two weeks, when it was killed. phragm pressed downward. Both pleural sacs converted into large abscess cavities, surrounded by thick pyogenic membranes, and distended with a thin, milky fluid. Both lungs compressed into a very small space. Pericardium and epicardium covered with purulent exudate.

No. 274 received 1 cubic centimeter of the suspension into the Exudative peritonitis, Dead in twelve hours. abdominal cavity.

pleuritis, and pericarditis.

No. 275 received into the right lung 14 cubic centimeters of the suspension. Dead in sixty hours. Double exudative pleuritis and pericarditis. Right lung almost entirely necrosed; the left has a typical pneumonia in principal lobe. Intense catarrhal inflammation of the stomach.

II. Another outbreak of swine disease among penned pigs not far from the Station, during November, 1888, deserves a brief description here, because of the very curious and instructive fact that swine plague occurred in one pen and hog cholera in another; nor was it possible to find hog-cholera germs in the swine plague pigs, or swine-plague germs in the hog cholera pigs. The details as regards the characters of the surroundings, the pens, etc., must be reserved for future publication.* A sow in one of the pens became sick November 8, and died suddenly next day. It had seven pigs seven weeks old, small for their age. All of these died in the space of four days, from November 9 to November 12, inclusive, and all but two were examined. The disease in these five cases was very much alike. The lungs were hepatized, the hepatization involving from one-half to two-thirds of the entire lung tissue, and invariably the dependent portion. The hepatization was quite firm, varying from a granular, grayish-red, mottled appearance to an occasional hemorrhagic infiltration.

Exudative pleuritis extending to the pericardium was present in every case. The stomach was usually contracted, empty, containing a bilious, catarrhal coating. The liver was unusually firm to the touch. The large intestine more or less hyperamic or pigmented, with slight roughening (necrosis?) of the surface in one case. There was not a sign of ulceration in any of these five cases. Mingled with the feces in several instances were masses of a soft, pale, yellowish color, which were probably exudates from the congested membrane. Careful bacteriological examination of the spleen, liver, lungs, and pleura resulted in finding swine-plague germs in every case. The hog-cholera germ was conspicuous by its absence. It is difficult to see how the disease in these cases can be credited to anything but the swine-plague germ. The hyperemia of the large intestine, which might have resulted in croupous or diphtheritic inflammation later on, may be explained by the swallowing of the virus either as it came from the bronchial tubes or as it was mixed with the food by the nasal discharges and feces of the diseased animals.

In another pen, but not in communication with the last, were five pigs recently purchased (in October). Three died, of which one was examined. The two remaining sick ones were taken to the Station, and they, together with the viscera of the one examined, were made the starting point of a typical hog cholera outbreak. The one examined was affected with extensive necrosis and ulceration of the cacum and colon, hemorrhagic lymphatics, scattering foci of hepatization in the lungs without pleuritis. In the various organs, including the lungs, hog-cholera bacilli were present in large numbers. No swineplague germs detected.

In a contiguous pen one pig died. This proved to be a case of hemorrhagic hog cholera without lung disease. Beginning necrosis, with hyperæmia in the intestine, hemorrhagic kidneys and lymphatics, and hemorrhages in different parts of the body. In this case only hog-cholera bacilli were found. The other pens on the farm remained free from disease.

If we sum up the result of the investigations we have five animals in one pen affected with extensive lung disease, which is associated with swine-plague germs only. We have two other pens, not in communication with this one, affected with hog cholera only. These facts demonstrate as clearly as any which we have thus far been able

*See foot-note to preceding outbreak.

to obtain that swine plague or infectious pneumonia may appear as an independent disease, fraught with a high mortality.

In connection with these investigations a few facts which may be of interest to those who may engage in this work in different parts of our country are briefly given. The swine-plague germs found in these two outbreaks differed considerably in their pathogenic power. In fact they must be regarded as distinct varieties in this respect. The germ obtained from the mixed outbreak first described was sufficiently virulent to kill rabbits in from sixteen to twenty hours, even after the slightest prick of the lancet upon which a minute speck of the germ growth had been deposited. In all the organs of the dead animal the germs were present in large numbers. The germ obtained from the outbreak just described differed in causing death in from three to seven days. Instead of the septicemia and the presence of germs in the blood of all organs they were restricted more or less to the peritoneal or pleural cavities, or to both, where they produced exudative inflammation.

In swine in the earliest acute cases of swine plague the lungs are practically a pure culture of the swine-plague germs, and from the pleuritic exudate pure cultures can always be obtained without resorting to plate cultures. Animals which succumb later on are less and less suitable for examination. The swine-plague germs are being destroyed in the lung tissue by the secondary processes of degeneration going on, and their place is taken by various bacteria from the air passages, which have no causal relation to the disease. The pleural cavities are lastly invaded by bacteria from the dead lung tissue, and this invasion may even extend to the spleen and other organs. The lesson to be drawn from these facts is obvious. In any outbreak all the animals should be examined and the investigation should never be limited to a few cases from a miscellaneous variety of epizootics. The chances of being misled are particularly great in the study of swine plague, unless we trace the disease from the earliest to the last cases, which is equivalent to saying from the most acute to the most chronic. Unfortunately for the investigator the existence of disease is rarely reported until a number of animals are dead, and these among the best cases for study which the whole epizootic has to offer. Another fact to be borne in mind by the investigator is the comparative uselessness of gelatine for cultivations. Neither of the two varieties of swine-plague germs described could be made to grow upon this medium with any degree of certainty.

Lung worms associated with these outbreaks of swine plague.The autumn of 1889 seems to have been very favorable to the lung worms (strongylus paradoxus), for most of the pigs of the swine plague outbreaks were infested with them. They were, as a rule, limited to the air tubes of the large principal lobe of both lungs. They were frequently so numerous as to completely occlude the principal bronchus and collateral branches. The resulting pneumonia was limited to the posterior (caudal) extremity of the lobe and to scattered regions through which the plugged branches passed. In fact, in a few cases examined from another outbreak, they were so numerous as to become a sufficient cause for all the lung disease observed. It is of considerable importance to determine how far the lung worms in their migrations may be held responsible for carrying disease germs into the lungs. In the epizoötics of swine plague the pneumonia caused by the worms was limited to the caudal tip of the principal lobe, while the infectious pneumonia invades the small an

terior lobes first, then the principal lobe. If, therefore, there exists any relation between the lung worms and the swine plague at all, it must be regarded as indirect. The life history of these parasites, by reason of their widespread destructive presence in certain seasons of the year, demands careful investigation. Experience at the Bureau Station seems to show that swine kept off the ground in pens do not become infested with these parasites, and this experience is worthy of more careful observation.

INVESTIGATIONS OF TEXAS FEVER.

Since the introduction and development of better methods in the study of micro-organisms, it seemed desirable to make more careful and elaborate investigations of this disease in order to determine if possible its nature and cause, and to derive therefrom rational means of prevention in addition to those already well known and applied. The difficulties in the way of such investigations are insurmountable, unless cases of the disease can be obtained which are within reach of a well equipped laboratory where the more delicate methods of research may be applied. The material at the disposal of the laboratory has therefore been very meager, in spite of continued efforts to obtain it during the season when it is most apt to appear north of the permanently infected area.

During the summer of 1888 about five cases were examined. The disease had broken out in Maryland, about 60 miles from the laboratory, and in spite of the care exercised in hunting it up only five cases fell into the hands of the inspector in a condition fit for examination. The various organs were brought in specially devised refrigerator cans to the laboratory, where they were subjected to a careful microscopical and bacteriological examination. The result of this work was in general negative. The internal organs were free from bacteria so far as the microscope and cultivation were able to go. At the same time investigations conducted in this manner were open to many objections, and during the summer of 1889 it was decided to produce the disease at the Experiment Station of the Bureau and thus have cases under observation from the beginning of the infection. Cattle from North Carolina, brought to the station during the last week in June, infected the pasture there so that the first native animal died late in August. Another importation of North Carolina cattle, late in September, was equally successful in giving rise to a second outbreak of the disease.

During the entire season eleven head of exposed native cattle died. Besides these fatal cases a number of cases which terminated in recovery came under observation. The symptoms and lesions may be very briefly summarized.

The first indication that the disease had entered the system and was there unfolding its destructive activity was a continuous high temperature, fluctuating very slightly and subsiding only when death or recovery ensued. The temperature rose from 101°-102° Fahrenheit to 106-107° Fahrenheit, and in the fatal cases remained high from four to fifteen days. After a variable number of days the high temperature was accompanied by general weakness lasting but a few days, when death ensued. A few days before death the urine became more or less deeply colored with hæmoglobin, and in nine out of eleven cases the bladder after death contained deeply tinged urine. In the tenth case hæmoglobinuria was present three days be