18 CANINE DISTEMPER 
in the respiratory tract, producing often a septicemia, 
and in all cases a profound toxemia. Many of the 
animals would die with no symptoms other than those 
of an acute intoxication—namely, a rise in temperature, 
followed by a sudden fall, loss in weight, and severe 
prostration, with death within a few days. The relation- 
ship of the organism to distemper has been shown by 
means of agglutination, complement fixation, and other 
specific tests, so that proof as regards the specificity of the 
organism is not lacking. It is also of interest to know 
that this germ will produce a disease similar to distemper 
in other animals, such as the rabbit; guinea-pig, cat, 
monkey, and ferret, and when this became recognised, 
the name B. bronchicanis was changed to B. bronchi- 
septicus.” 
Exotoxin Theory.—If this organism is to be regarded 
as the specific cause of distemper, an explanation may 
be invited as to how the germ-free pericardial serosity 
taken from a distempered dog can, when inoculated into 
a healthy dog, produce identical symptoms. For answer, 
one is led to conclude that the B. bronchisepticus located 
in the trachea and bronchi generates an exotoxin which 
circulates in the blood, and which, if individually em- 
ployed, will set up precisely the same malady as though 
the actual causal organism were also present. In the 
various diseases caused by bacteria, changes frequently — 
occur in certain organs which are unassociated with the 
presence of the bacteria; these are produced by the 
action of bacterial products circulating in the blood. 
Two good examples of pathogenic organisms which 
produce soluble toxins are the B. diphtheri@ and B. tetani. 
In these and similar cases, when broth cultures are 
rendered germ-free by a bacterial filter, toxic fluids 
are obtained which, on injection into susceptible animals, 
reproduce the highly characteristic symptoms of their 
corresponding diseases. 
Exotoxins may be distinguished from endotoxins, 
See Te 
