Annual Report of the Royal Veterinary College. 135 
The Diagnosis op Tuberculosis. 
During the past year a most extensive series of experiments and 
observations have been made regarding the diagnosis of tuberculosis. 
It is now generally recognised that tuberculosis is a contagious dis- 
ease, and that its present alarming prevalence among cattle is due 
to the transmission of the germ from diseased to healthy animals. 
There are some who believe that this transmission in many cases 
takes place from the bull or the cow to the calf, before the birth of 
the latter, while others consider that in all but an insignificant pro- 
portion of cases the disease is contracted after birth, through co- 
habitation with cattle already affected with tuberculosis. No matter 
which of these views regarding the mode of infection is accepted, the 
immense importance of being able to detect the disease in its early 
stages is apparent. If the disease (and not the mere predisposition 
thereto) is actually transmissible from parent to offspring, every 
breeder will naturally wish to know which animals of his herd are 
already infected, so that he may avoid breeding from them ; on the 
other hand, if every tuberculous animal is a source of danger to its 
companions in the same stock, the hope of eradicating the disease 
will lie in being able to detect it at an early stage, so as to get rid 
promptly of the source of infection. 
It must be frankly confessed that hitherto anything approaching 
a certain diagnosis of tuberculosis in cattle in its early stage has been 
impossible. This has been due to the circumstances of the case, and 
not to any inferiority of skill on the part of veterinary surgeons. In 
the vast majority of cases the disease has its starting point in parts of 
the body so deeply situated as to be entirely removed from exami- 
nation during life. Added to that there is the fact that these pri- 
mary seats of the microbe may be pretty extensively diseased without 
entailingany very great deterioration of theanimal’sgeneral condition. 
Whenever the disease has seriously invaded a vital organ, such as 
the lung or the bowel, the disorder can generally be diagnosed with 
more or less probability, and sometimes with absolute certainty, but 
before that becomes possible the affected animal may have done 
much mischief by sowing the seeds of the disease in some of its com- 
panions. 
During the past year various suggested methods of arriving at an 
early diagnosis were put to the test of experiment. Microscopic 
examination of blood, milk, mucus from the throat, &c., and inocu- 
lation of these same materials from animals proved subsequently by 
post-mortem examination to be tuberculous, showed that none of 
these procedures could be relied upon to point out the existence of 
the disease in more than a very small proportion of cases. Fortu- 
nately, much more encouraging results have been obtained in an ex- 
tensive trial of Koch’s tuberculin. 
Tuberculin is a liquid which contains in solution certain sub- 
stances manufactured or excreted by the tubercle bacillus when arti- 
ficially cultivated. Koch discovered that this material exercises a 
much more powerful effect in tuberculous than in non-tuberculous 
