687 
ON MURRAIN, OR THE VESICULAR EPIZOOTIC. 
under its influence. But, whatever may have been the mode of its 
origin or introduction, it soon made itself widely known throughout 
England, and rapidly spread both to the west and to the north. 
Within a year of its first appearance in England, it had committed 
extensive ravages in Ireland, and had engaged the attention of 
many practitioners north of the Tweed. 
The severity of the vesicular epizootic has varied much in diffe- 
rent parts of the country. In some parts of England, and espe- 
cially when it first appeared, fatal cases were not of infrequent 
occurrence ; the duration of the disease was long, and the cases 
tedious and troublesome. More recently, however, it has become 
of a less malignant type, and also of less general occurrence. In 
Scotland it never assumed such a formidable character, nor diffused 
itself so widely as in the southern parts of the island. Indeed, in 
some districts the malady was exceedingly mild. A slight lame- 
ness and tenderness of the mouth were observable for some days, 
and then the animal was well again. In many such cases the loss 
of condition was but slight, and was compensated for by the sub- 
sequent improvement; for the disease in this mild form seemed to 
increase the vigour of the system, and the tendency to grow and 
to accumulate fat. 
After the disease had existed in the country for about two years, 
its virulence gradually abated, and the number of cases also became 
less numerous. This phenomenon seems to attend most epidemic 
and epizootic maladies. At first their malignity is very great, and 
their ravages very general ; but after a time the cases diminish in 
severity and in frequency of occurrence, and the disease appears to 
lose its power of propagation and many of its epizootical character- 
istics. The explanation of this may be, either that the proximate 
cause has lost its energy, or that the predisposition to receive and 
mature it has passed away. In the vesicular epizootic, and other 
eruptive fevers, animals having previously had the disease are less 
liable to a second attack ; and thus, when the disease has existed 
in any locality for a considerable time, the number of cases natu- 
rally becomes much diminished. 
During the last few years, cases of the vesicular epizootic have 
been of comparatively infrequent occurrence ; and, although the 
disease has appeared in a few stocks in various parts of the island, 
it has seldom tarried long, or prevailed over any great extent of 
country. During the spring months of the present year (1849), 
however, the disease appears to have been more general than usual, 
and it is at present reported to exist in many parts of Scotland, and 
to have spread extensively both amongst cattle and sheep. 
Causes . — The causes of the vesicular epizootic, and the circum- 
stances which lead to its prevalence, or which retard or arrest its 
