238 VETERINARY HYGIENE 



constant danger that infection may spread indirectly from the old 

 herd to the new one in process of formation if these are kept in 

 adjacent buildings. In the second case the danger arises from the 

 fact, of which there is plenty of evidence, that the ordinary sub- 

 cutaneous test with tuberculin cannot be relied upon to provoke a 

 distinct temperature reaction in every infected animal. This was 

 one of the reasons assigned by Bang for abstaining from carrying 

 out a preliminary test of the herd with a view to separating the 

 infected from the non-infected. For reasons already stated it 

 would in many English herds be hopeless to attempt to deal with 

 the disease if all the animals already in the herd had to be left 

 untested and regarded as diseased. It may, however, be asked 

 whether the introduction of new methods of employing tuberculin 

 has not in a large measure removed the objection to carrying out 

 a preliminary test of the entire herd and accepting non-reaction as 

 reliable evidence of freedom from tuberculosis. The writer's 

 experience leads him to think that this question ought to have an 

 affirmative answer. There is good reason to believe that by com- 

 bining the ophthalmic and intradermic methods with the ordinary 

 subcutaneous test the failures of tuberculin can be reduced nearly 

 to the vanishing point. The combined method of testing marks a 

 great advance, although none of the new methods used alone gives 

 as low a proportion of errors as the original subcutaneous test." 



In addition to the use of tuberculin, the isolation of reactors, 

 &c., the following rules of hygiene must be carefully attended to. 

 Byres must be properly constructed (see page 165) ; especially to 

 be avoided is the system whereby stalls are arranged in rows so 

 that the cows are facing one another. The exclusion of affected 

 animals however, though infection is only revealed by a reaction 

 of tuberculin, is the first consideration. Tuberculosis may spread 

 under the best of hygienic conditions, but more quickly and more 

 certainly in the foul byres too frequently seen in and about cities. 

 The wall facing the cows, the partitions and feeding passage, if 

 one exists, must be washed down at least once a week. The 

 mangers must be cleaned out daily, a vigorous application of hose 

 pipe and brush will rid a byre of enormous quantities of virulent 

 material, which would, if left in situ, become partially dried and 

 spread about the building, infecting all and sundry. 



From the point of view of the spread of the disease to man, 

 the most dangerous animal is the cow affected with tuberculosis 

 of the udder. Milk from a tubercular udder always contains 

 tubercle bacilli, and owing to the fact that the disease in the udder 

 is always very slowly progressive, there is probably in every case 



