LURE RCULOSIS IN CATTLE, 15 
a slight extent that only a very minute lymphatic gland may 
be infested with the disease. In some cases a swollen gland 
no larger than a pea, and sometimes even smaller, will be the 
only evidence of the presence of tuberculosis. Now, in such 
cases it is, of course, very evident that an inspector who has 
many hundreds of animals to examine in a day and does his 
work somewhat hurriedly will overlook many instances of such 
incipient tuberculosis, while a second inspector, who has more 
time and a smaller amount of work to do, will discover them. 
The care that is given to the inspection, then, will affect the 
statistics very materially, and the figures that come from one 
slaughter house may therefore be absolutely incommensurate 
with those that come from the second. The results are 
affected, thirdly, by the personal inclination of the inspector, 
a factor that always enters largely into the statistics. One in- 
spector desires to prove the wide prevalence of the disease and 
examines the carcasses much more carefully than the second, 
who is either indifferent, or desirous to reach the conclusion 
that tuberculosis is not very prevalent. The former will hunt 
carefully for all cases where even a small gland may be in- 
fested; the latter will overlook them. The result is that it is 
almost impossible to compare the statistics given at one 
slaughter house with those obtained at a second. 
A second series of facts that very much influences these 
statistics is connected with the age of cattle that are brought to 
the slaughter-house. It is a well demonstrated fact that in 
Europe old cows are very commonly tuberculous, some 
veterinarians going so far as to say practically always affected 
with tuberculosis, while young animals are much more rarely 
affected. Now, if one slaughter-house chances to have only 
old cows brought to it for slaughter, while a second is con- 
cerned chiefly with younger animals, the statistics obtained by 
the one will be radically different from the other’s, and inas- 
much as no record will be commonly made of the age of the 
animals slaughtered, the statistics will give very erroneous con- 
clusions. For these reasons, then, we see that statistics, even 
derived from such a clear method as examinations of car- 
casses, must be looked upon with suspicion. 
A second method of determining the presence of tubercu- 
losis is by the use of tuberculin. As is well known by every 
farmer, the inoculation of an animal with tuberculin will detect 
very accurately the presence of this disease, and will show its 
presence in living animals in many cases where clinical symp- 
