Diagram B when the production, and, consequently, the stock of hogs had reached the highest point. The large stock of hogs then on hand evidently was the means of furnishing a home market for the corn and caused an advance in price when under other conditions there would have been a further decline. The price of corn is therefore governed primarily by the law of supply and demand, but it may also be influenced by the financial condition of the country, the purchasing power of money, and the relative supply of other cereals, and perhaps by other conditions. There is one other point deserving of consideration in this connection. It is a very common custom when corn advances in price for farmers to hurry their hogs to market and reduce their breeding stock. A glance at the table demonstrates the existence of this custom, for we see that the hog product was invariably decreased as the price of corn advanced and when the price of corn declined the hog product again increased. This fact has led the writer to inquire if there was in reality any less return to the feeder for each bushel of corn when the price was high than when it was low. To determine this the three years 1874, 1881, and 1887, were taken, at which the ascending lines were at their highest point, and it was found that the average price of corn for those years was 57.5 cents and the average price of hogs $5.92—that is, the value of a bushel of corn was equivalent to the value of 9.54 pounds of hogs. Taking now the four years 1872, 1878, 1885, and 1889, when the descending lines reached their lowest point, we find the average price of corn to have been 33.2 cents and the average price of hogs $3.47. In this case a bushel of corn is equal in value to 9.56 pounds of hogs, or practically the ratio is exactly the same as when corn was high. It appears that the best returns for hogs in comparison with the price of corn were received during the intermediate years between the extremely high or extremely low prices. Taking the eight years 1873, 1876, 1877, 1879, 1880, 1883, 1884, and 1886, we find the average price of corn to have been 39 cents and the average price of hogs $4.59. For these years it will be seen that 8.5 pounds of hogs brought as much as a bushel of corn. These facts are important as indicating the proper course for the farmer to pursue under the varying conditions which are here considered. Their application is so plain to those that are interested that it is not necessary to go into greater details in this report. UNITED STATES CATTLE QUARANTINE. The superintendents of the various neat cattle quarantine stations report the names of the importers and the number and breed of each lot of animals imported during the year 1890, as follows: Date of arrival. Station for the port of Baltimore, St. Denis, Maryland. [Dr. A. M. Farrington, acting veterinary inspector.] Name and post office address of importer. Port of shipment. Name of breed. No. of animals. 1890. Mar. 17 S. C. Kent, West Grove, Pa. Liverpool.. Guernsey. 62 Station for the port of New York, Garfield, New Jersey. Station for the port of Boston, Littleton, Massachusetts. Station for the port of Boston, Littleton, Massachusetts. The following shows the whole number of cattle and sheep received at the various stations from January 1, 1889, to January 1, The following brief account of the investigations conducted under my direction into the nature of the infectious diseases of animals has been prepared by Dr. Theobald Smith, who is in charge of this branch of the work of the Bureau of Animal Industry. All minor details, as well as the greater part of the autopsy notes, have been reserved for special reports, and only the most important results are given in this place. INVESTIGATIONS OF TEXAS CATTLE FEVER. The investigations into the nature and causes of Texas or southern cattle fever have been busily pushed during the summer of 1890, and some very important advances made which are destined to be of great practical importance. During the suminer of 1888 much time was spent in determining 729 12 whether or not any specific bacteria are the cause of this disease as they are of a host of human and animal infectious diseases. This was the more necessary inasmuch as former observers have always described bacteria of one kind or another associated with it. But no bacteria could be found in the bodies of animals which had succumbed to Texas fever excepting those which quite invariably multiply in dead bodies after a time and have no significance whatever. At the same time the writer came to the conclusion that the disease was confined to the blood and consisted essentially in a breaking down of the red corpuscles. During the summer of 1889 arrangements were made by which the disease could be studied near the laboratory in Washington, and, as 'reported last year, a parasite was found within the red corpuscles whose presence could only mean the breaking up of the corpuscle itself sooner or later. This discovery was adapted to explain satisfactorily the various lesions observed, as well as the great reduction in the number of corpuscles observed in those cases which died after prolonged disease or which ultimately survived. In some of these cases the blood is watery; it has in fact scarcely any color remaining. This condition was expressed mathematically by counting the number of blood corpuscles. Thus in most cases before death the number of corpuscles was but one-sixth of the number normally present in the body. When we contemplate the very important functions of these elements we need not be surprised at the serious effects resulting from loss to the body, within one or two weeks, of five-sixths of its corpuscles. During the present year the disease was produced at the Experiment Station by the importation of North Carolina and Texas cattle and the investigations continued. The work was sufficiently extensive to occupy most of the time from July to December, while the examination of preparations and other work connected with this subject occupied much of the writer's time last winter and will of necessity require much additional labor this winter. During the summer about fifty-three native animals, distributed around in various experimental inclosures at the station, received more or less careful attention. The temperature of all was taken every other day by Dr. Kilborne to detect the beginning of the dis Of these about twenty-four either succumbed to Texas fever or else were killed in a dying condition. These cases were subjected to a careful post-mortem examination, and the internal organs underwent a careful microscopic scrutiny at the laboratory. The surviving animals were examined at different intervals of time more especially with reference to the condition of the blood. The blood corpuscles were counted and carefully examined with reference to the presence of the Texas fever parasites in order to determine the presence of any disease and the progress it was making. Those animals that died were also examined more or less frequently during the course of the disease in the same way. It was found moreover that these blood examinations were absolutely necessary in many cases to detect any disease whatever, and they put the field experiments, to be outlined later on, on a positive basis. The examination of the internal organs, such as the spleen, liver, and kidneys, from those animals that died of Texas fever showed the presence of the blood parasite described last year in every case; in some in such enormous numbers that every other blood corpuscle appeared infected. In the course of the disease the parasites were detected in many of the cases examined. They were also present in the circulating lood one or two days before the animal died. This parasite, which, as has been stated before, does not belong to the bacteria but to the protozoa, received considerable attention during the summer. It has appeared under several forms, and distinct amoeboid movements of the largest forms were seen within the red corpuscles whenever the preparation was maintained above a certain temperature. The work of the summer has thus confirmed that done during the two previous summers. There can be no doubt of the existence of genuine parasites within the red corpuscles and their destructive activity. THE RELATION OF TICKS TO TEXAS CATTLE FEVER. While the investigations into the nature of this disease were going on other equally important work was being carried on at the Experiment Station on the external characters of the disease. It is well known to those who have come in contact with southern cattle in summer that they are infested with the so-called cattle-tick, a pest belonging to the class Arachnoidea and to the family Ixodidœ. These ticks are carried north with cattle during the warm season of the year. When fully matured they drop off from the southern animals, lay their eggs on the ground, and perish. The young ticks are hatched within fifteen to thirty days after the eggs are laid and at once get upon the cattle where they become mature within twenty to thirty days to again drop off, lay their eggs, and die. This process goes on continuously until the cold weather comes. At various times and in different parts of the country it has been suggested that the ticks were the cause of Texas fever in northern cattle. This inference was undoubtedly suggested by the fact that nearly all cattle that die of Texas fever are observed to have these ticks of various sizes attached to the skin. Moreover the disease only makes its appearance after the young ticks have attached themselves to cattle. Though this was purely a post hoc propter hoc inference, it was nevertheless true, as the experiments to be recorded will amply prove. During the summer of 1889 Dr. F. L. Kilborne, in arranging the various inclosures at the Experiment Station for the exposure of native cattle to the infection of Texas fever, conceived the happy idea of testing this popular theory of the relation of ticks to the disease. This he did by placing southern (North Carolina) cattle with native cattle in the same inclosure and picking the ticks from the southern stock as soon as they had grown large enough to be detected on the skin. This prevented any ticks from maturing and infecting the pasture with the eggs and hence prevented any ticks from infesting native cattle subsequently. At the same time, in another inclosure, the ticks were left on the southern cattle. The natives in the latter field died of Texas fever; those in the former did not show any signs of the disease. Another experiment was made in September in the same manner by preparing three fields, one with southern cattle and ticks, a second with southern cattle from which the ticks were removed, and a third over which only adult ticks had been scattered. The result was equally positive. In the first field no natives died, but careful examination of the blood by the writer showed Texas fever in an un mistakable manner. In the "tick" field one animal died of Texas fever, and the examination of the blood showed that most other natives in the field were sick. In the third field containing southern cattle without ticks no disease could be detected. These two tests pointed directly to ticks as being in some way the cause of Texas fever. At the same time it was thought best to confirm these results by further experiments during the present year before other agencies could be eliminated. The immediate inference was that the ticks infect the pastures, and that in some unexplained manner the infection finds its way into the body of susceptible cattle. The preliminary conclusions deducible from the work of 1888 and 1889 can be formulated as follows: (1) Texas fever is a disease not caused by bacteria. Its nature can not be understood by supposing a simple transfer of bacteria from southern cattle to pastures and from pastures to northern cattle. (2) The cause is very probably a protozoon, with a more complex life history, living for a time within the red corpuscles of infected animals. (3) Southern cattle without ticks can not infect a pasture. (4) Ticks alone scattered on a pasture will produce the disease. The work of 1890 was planned to confirm or refute these preliminary conclusions and to furnish additional information. The fields were arranged as before. One contained North Carolina cattle with ticks, a second Texas cattle with ticks, a third North Carolina cattle without ticks, a fourth ticks only, and a fifth soil from the pastures of infected North Carolina farms. Other fields were also laid out to test questions which need not engage our attention in this brief survey. The results confirmed those of last year. The first animal to die was in the "tick" field, containing no southern cattle. No disease appeared in the soil field. Unfortunately, owing to the limited space of ground at our disposal and its barren, rolling character, ticks or eggs were washed during the very heavy rains of the summer from the tick field into the field containing southern cattle without ticks, although a wide lane intervened. The natives in this field thereupon all died of Texas fever. At the autopsy of these cases ticks were found attached to their skin in abundance. The disease caused by Texas cattle could not be distinguished in character from that which was produced by North Carolina cattle. These results similarly pointed to ticks as the cause. The precise manner in which they caused the disease was by no means clear, however. The theory which seemed for a time most acceptable was that the adult ticks as they dropped off infected the pastures with germs which they had taken in with the blood of southern cattle, and that the germs were introduced into the body of northern cattle with the food. At the same time no parasite could be detected in the blood of southern cattle examined at various times, on which fact I would lay no great stress, however. Of more importance is the peculiarity which is exhibited by this disease in its period of incubation, as it may be provisionally denominated, and which is opposed to this theory. Thus, when native and southern cattle are placed on the same pasture at the same time it will take from forty to sixty days for the disease to appear. After the disease has once shown itself fresh animals placed on the same pasture may die, according to our experience, within thirteen days after the begin |