State.Number
tested.		Number
tuberculous.		Per cent
tuberculous.
Alabama68,7721,0711.6
Arkansas5,917981.7
Colorado1,959763.9
Connecticut29,2864,69516.0
Delaware19,0032,13211.2
Florida56,5331,4382.5
Georgia46,5229982.1
Idaho57,7311,0521.8
Illinois92,7816,1126.6
Indiana142,8333,9912.8
Iowa158,5149,9586.3
Kansas64,3411,7962.8
Kentucky66,8391,4922.2
Louisiana36,3919812.7
Maine67,4061,7922.7
Maryland65,8885,4918.3
Massachusetts26,2972,3719.0
Michigan163,3235,3613.3
Minnesota240,8887,5553.1
Mississippi99,245503.5
Missouri196,2082,5871.3
Montana165,6403,3462.0
Nebraska125,1623,9473.2
Nevada29,5411,0423.5
New Hampshire16,6231,69710.2
New Jersey32,1842,5427.9
New Mexico3,897391.0
New York167,85223,07113.7
North Carolina64,0081,0981.7
North Dakota139,5014,1423.0
Ohio97,6124,4704.6
Oklahoma67,5222,4533.6
Oregon123,7922,5812.1
Pennsylvania102,4656,3226.2
Rhode Island3,4583389.8
South Carolina41,8687401.8
South Dakota43,4332,3535.4
Tennessee63,6319561.5
Texas61,9561,2562.0
Utah59,7115861.0
Vermont160,36111,4867.2
Virginia135,6773,8812.9
Washington154,2923,8642.5
West Virginia36,6037982.2
Wisconsin285,2698,1662.9
Wyoming22,8113221.4

Reports of tuberculin tests made on 400,000 cattle in the United States during the years 1893 to 1908 by Federal, State, and other officers with tuberculin prepared by the Bureau of Animal Industry show 37,008 reactions, or 9.25 per cent. These were mostly dairy cattle, and in some cases herds were suspected of being diseased.

Later reports of tuberculin tests made in the United States from July 1, 1917, to March 1, 1922, on 3,911,546 cattle by State, county, and Federal officers engaged in cooperative tuberculosis eradication work showed 153,046 reactions, or 3.9 per cent.

All cattle in the District of Columbia, numbering 1,701, were tested with tuberculin in 1909-10, and 18.87 per cent reacted. In 1909-11 herds in Maryland and Virginia supplying milk to the District of Columbia were tested, with 19.03 and 15.38 per cent of reactions, respectively, among 4,501 cattle.

All cattle in the District of Columbia were tuberculin tested in 1920-21, numbering 1,313, and 5 animals reacted, or 0.4 per cent, demonstrating that tuberculosis may be eradicated from all the herds in a circumscribed area.

The beef cattle of the United States show a much smaller proportion of the disease than dairy cattle, though the percentage of cattle found tuberculous in the Government meat-inspection service has increased considerably in recent years. This increase is due partly, but not wholly, to more stringent inspection. Of 7,781,030 adult cattle slaughtered under Federal inspection during the fiscal year ended June 30, 1911, 76,448 were found tuberculous, a percentage of 0.98.

From the statistics above referred to, and other data, it appears that in the more densely populated areas of Europe and America from 5 to 50 per cent of the dairy cattle are more or less affected with tuberculosis, while the proportion of beef cattle affected is distinctly less, ranging from 0.14 to 30 per cent. This difference is due to a number of causes. Beef cattle average younger when slaughtered. They are not so frequently stabled, and are for that reason less liable to infection, and as the males constitute a large proportion of this class of animals the effect of milk secretion in lowering the vital forces is not so apparent. In the United States it has been estimated that about 10 per cent of the dairy cattle are tuberculous, while only about 2 per cent of the beef cattle are so infected.

Cause and nature of the disease.—The cause of tuberculosis is the tubercle bacillus, which gains entrance to the body, lodges somewhere in the tissues, and begins to grow and multiply at that point. As this bacillus vegetates and increases in numbers it excretes substances which act as irritants and poisons and which lead to the formation of a small nodule, called a tubercle, at the point of irritation. As the bacilli are disseminated through the animal body they affect many parts and cause the formation of an enormous number of tubercles. By the union of such tubercles, masses of tubercular material are formed, which in some cases are of great size. The disease is called tuberculosis because it is characterized by the formation of these peculiar nodules, and the bacillus which causes the disease is for the same reason known technically as the Mycobacterium tuberculosis.

There are undoubtedly predisposing conditions which contribute toward the development of the disease; some of these are found in the animal body and others in the environment. An enfeebled condition caused by insufficient feed, exposure to great extremes of atmospheric temperature and insanitary surroundings, or the drain occasioned by heavy production of milk, appear to aid the development of the bacillus, and there is also a special individual susceptibility in some cases which may be otherwise described as an inability of the animal tissues to resist and destroy the bacilli when they have penetrated to the inner recesses of the body.