60 CANINE DISTEMPER 
Age at which to Vaccinate.—When our object in 
vaccinating dogs against distemper is one of prevention 
and not cure, we need to carry it out as early as possible, 
in order that the risk of natural infection before the opera- 
tion may be diminished. On the other hand, it is highly 
desirable that the pup should have been weaned, and 
become accustomed to its ordinary food and hardened 
somewhat to its new life. Thus the suitable age would 
appear to be seven or eight weeks, though there is no 
reason why it should not be attempted later in life, 
except the increasing danger of infection prior to inocu- 
lation; for it is well known that if a latent infection 
exists when vaccination is performed, the addition of 
a little more toxin to an already contaminated system 
might overpower the existing defensive forces, and 
perhaps cause a very alarming disturbance. 
The puppy, having received its series of two or three 
injections, should be isolated for a full fortnight to 
permit of immunity becoming firmly established, and 
certainly should have been excluded from all possible 
sources of contagion during the whole period of his 
treatment. No doubt unfortunate sequele have often 
attended the exposure of a puppy to infection too soon 
after inoculation; even exposure to chills or fatigue 
would render the animal more liable to contagion by the 
temporary lowering of vitality produced. : 
Further, to obviate accidents, it is advisable, in cases 
where the dog is known to have been exposed to the 
contagium of distemper, to give a dose of immune serum 
before, or along with, each prophylactic dose of vaccine, 
to produce an immediate passive immunity. Previous 
inoculation with serum enables all animals, even those 
which are in a state of latent infection, to receive vaccine 
without any danger. 
In fact, this method might well be adopted as a routine 
