734 
SMALLPOX AMONG SHEEP IN WILTSHIRE. 
introduction of a contagious disease into a given locality, 
under certain conditions, has led to a formidable extension of 
the disease; that the introduction of a like disease in another 
locality, under different circumstances, or into the previous 
locality at a different period, has been followed by no evil 
consequences, the disease dying out in the individuals pri¬ 
marily affected; and that the most efficient means of protection 
from a contagious affection, even when pestilential, has been 
the removal of the conditions fostering the development 
of the disease, not the attempted exclusion of the disease 
itself. 
The conclusion is obvious, that any system which may be 
adopted for the prevention of the extension of a contagious 
disease will, in all probability, entirely fail, unless it provides, 
not only for the exclusion of the disease, but also for the 
removal of the whole of the conditions upon which the further 
development of the malady depends. 
That the latter is by far the most important point to attend 
to, a little reflection will show, even if the vast experience of 
many people and many epidemics and epizootics does not 
alone suffice to convince. Consider for a moment the mode 
of manifestation of all great epidemics. A few’ scattered cases 
of the disease at an interval of, perhaps, several months—a 
few isolated instances of small but significant outbreaks— 
these are the usual forerunners of the great outbreak, and are 
commonly neither heeded nor even known. But to make a 
provision for the exclusion of the possibility of contagion 
during this period would be permanently to interpose so 
serious an impediment to commerce and intercourse, as to 
make both the one and the other well nigh impracticable; 
and this for an end the attainment of which is extremely 
doubtful, if not altogether improbable. Let this consideration 
be applied to efforts intended to prevent the introduction of 
disease from without into the boundaries of a kingdom. And 
now of contagious disease within the limits. When diphtheria 
first attracted notice in this country, during the recent 
epidemic, the then known times and places of appearance of 
the disease gave rise to the belief that it had first broken out 
in the south-eastern counties, and from them gradually 
spread by contagion over the remainder of the kingdom. 
The outbreak was, moreover, thought to be connected with a 
formidable irruption of the disease which had previously 
occurred in Boulogne. It was a noteworthy fact, that one of 
the earliest cases recorded on the south-eastern coast was 
in a household which had but recently crossed the channel 
* 
from the infected French city. Here, then, the fact of diffusion 
by contagion seemed most probable, if not clear. It is now, 
