No. fi. DEPARTMENT OF AGRICULTURE. 127 



gi-adt'.s, or iiali\c'S is sliuwn most clearly by the statistics ol' the 

 iiis[)ections made undei- the auspices of the State Live Stock Sani- 

 tary Board. Tlie worst infected herds tliat have been found In 

 JVnnsylvania were herds of natives. Additional proof is furnislied 

 by the fact that there are a number of well-established herds of 

 Jersey and Guernsey cattle that are, and always have been, free 

 from tuberculosis. These herds were formed many years ago, 

 before tuberculosis became a prevalent disease and it hai^pened 

 that they were composed of aninuils free from tuberculosis. Great 

 care has been exercised in purchasing additions to these herds. 

 Added animals have been few^ in number and generally bulls pur- 

 chased when calves. In this way the introduction of animals suf- 

 fering with and scattering the seeds of tuberculosis, has been 

 avoided and the herds have remained wholly exempt. 



Through the operation of a similar cliain of circumstances some 

 large districts of the State have remained clear of tuberculosis 

 of cattle. These districts are usually interior valleys, more or 

 less isolated, into which cattle may not readily be shipped, and 

 from which the current of the cattle trade is outward. Since these 

 districts were stocked with cattle long ago, before tuberculosis was 

 prevalent, they were stocked wdth cattle free from this disease and 

 it has happened that the few animals taken in, have not carried 

 infection. But, without repressive measures, all of these sections 

 would, in time, have been reached by tuberculosis precisely as many 

 others have been reached. In some instances, that have fallen 

 under my observation, the introduction of tuberculosis and its 

 spread in a region formerly free from it, have occurred so recenth^ 

 that it has been possible to trace the process step by step. It has 

 been possible, in some instances, to ascertain that, for a long series 

 of 3-ears, there has been no disease corresponding to tuberculosis 

 among any of the cattle on a large group of neighboring farms. 

 Later, animals decline and die wdth tuberculosis in herds on several 

 of these farms and inspection show^ed the disease to be widely dis- 

 tributed. Investigations in such cases have sometimes shown that 

 the disease started in a cow brought from without, possibly from 

 some famous pure-bred herd The cow seemed to be healthy when 

 she was purchased and afterwards developed a wasting disease, 

 the description of which enables one to identif}^ it, with a practical 

 certainty, as tuberculosis. Subsequenth', other cattle in the same 

 herd developed a similar condition and the bane was carried to 

 other herds in the neighborhood through the sale of cattle from the 

 one first infected. In the beginning of the infection of the cattle 

 of a region, and for a number of years, tuberculosis spreads very 

 slowly. The disease is propagated chiefly by contact. Therefore, 

 as one cow usually comes in contact with but a limited number of 



