BY PROFESSOR CROOKSHANK. 33^ 



exception of two, in which there were suspicious symptoms. 

 All reacted to the test of tuberculin, and were killed for 

 examination. In every animal there were indications of 

 tuberculosis ; a still greater excitement was caused by the 

 testing of Qaeen Victoria's cows at Windsor. Thirty-two 

 gave a reaction, three were doubtful, and five were apparently 

 healthy. When the animals were killed and examined, thirty- 

 six were found to be tubercular. Equally startling statistics 

 were collected from other quarters. Of cattle tested in 

 various parts of England and Scotland, as many as 31 per cent, 

 reacted. In London, 25 per cent, of cattle slaughtered under 

 the Pleuro-pneumonia compulsory slaughter order, were found 

 to be tubercular, and in some herds as many as 30 per cent, 

 to 40 per cent. It was estimated that about 20 per cent, of 

 milch cows in towns in England were tubercular. In Germany, 

 the returns from the abattoirs were in many cases even higher. 

 You are now in a position to realise the sensation caused by 

 Dr. Koch, when he announced at the last Congress of Tuber- 

 culosis in London, that human and bovine tuberculosis were, 

 after all, not inter-communicable. This statement upset the 

 policy of the medical department of the Local Government 

 Board. It paralysed the law, for it was quite impossible in 

 the face of such a statement, to obtain a conviction before 

 magistrates ; and it destroyed many arguments upon which 

 the crusade was being instituted for the eradication of human 

 tuberculosis. Many, however, hailed the announcement with 

 unqualified satisfaction ; for if Dr. Koch's views were correct, 

 then one of the channels of infection which was supposed to 

 exist was eliminated, and an imaginary danger removed from 

 our midst. In order to follow the controversy which ensued, 

 I must refer to Dr. Koch's researches in some detail, so that I 

 may be able to make clear the points at issue, and compare 

 his work and conclusions with the experiments and opinions 

 of others who have investigated the subject. Dr. Koch's ex- 

 periments were carried on for about two years with the co- 

 operation of a very distinguished veterinarian. Professor 

 Schutz, of Berlin. In various ways they inoculated 19 cattle 

 with tubercular virus from a human source, and none of the 

 cattle developed any symptoms of disease. On the other hand, 

 cattle inoculated with virus from a bovine source, suffered 

 without a single exception from the severest tubercular dis- 

 orders of the internal organs. Dr Koch was forced to the 

 conclusion that human tuberculosis differed essentially from 



