TUBERCULOSIS. 
595 
the public in general this secondary idea had become so firmly 
impressed upon their minds that the rigid laws could no longer 
be enforced. Up to the year 1783 the contagious theory of tu¬ 
berculosis had many advocates, yet the balance of opinion was 
on the opposite side. Even those who affirmed the contagious¬ 
ness of the disease were in the dark as to its true cause. Some 
fault in the animal’s hygiene was, as a rule, the attributed cause, 
the nature of which was not known. The first intimation that 
some irritating or infectious element was contained in the milk 
of cows suffering with the disease is due to Gerlach, late direc¬ 
tor of the Royal Veterinary Institute of Berlin. 
\ illemin, Klebs, Orth, Buhl, and others, demonstrated, dur¬ 
ing the period from 1857 to 1864, beyond a doubt that the ele¬ 
ments from tubercular diseased organs contained some peculiar 
infectious material, and when inoculated into other animals ex- 
peiimentally was capable of producing the same disease. As a 
result of these experiments Villemin announced, in i864,that tu- 
bei culosis was a specific disease, and due entirely to some 
specifie cause fiom without the organism. The true cause of the 
disease, however, remained shrouded in darkness until Koch, in 
1882, announced his discovery of the bacillus of tuberculosis. 
Since that time all of the experiments have served to strengthen 
Koch s statement that the bacillus is the sole cause of tuberculo¬ 
sis. 
The manner in which the disease spreads from one animal to 
anothei, and from the lower animals to the human family, and 
dice versa is an interesting one and demands our serious consid¬ 
eration. 
As all, or most, warm blooded animals are subject to the dis¬ 
ease, the germ must necessarily have a large number of carri¬ 
ers. Before entering into a discussion of the manner in which 
the disease is spread it may be stated that the germ may enter 
the system of the healthy subject through the respiratory, diges¬ 
tive and sexual organs and skin. It may also enter the unborn 
foetus through the dam. It most frequently, however, enters 
the system through the digestive and respiratory organs. 
