HUMAN AND ANIMAL VARIOLAS. 
381 
opinion, but know for a well-established fact that he was justified 
in that o inion ; inasmuch as horses suffer from a malady closely 
resembling the so-called “ grease ” (which is simply a kind of 
catarrhal inflammation of the sebaceous follicles of the skin at 
the lower part of the limbs), and that this malady is transmissible 
to the cow and to mankind, producing a train of symptoms so 
exactly like vaccinia that no material difference can be discerned 
between the two maladies. 
Jenner was too serious a philosopher and exact an observer to 
make light assertions or superficial examinations, and he only 
erred when he stated that the one source of cow-pox, and even of 
small-pox, was to be found in the horse. He was absolutely cor¬ 
rect as to a particular cutaneous disease of the horses’ limbs being 
transferred, by means of human hands, to the cow’s udder, and 
there producing cow-pox, which again could be communicated to 
people and protect them from small-pox. The facts, accidental 
a,nd experimental, upon which he based his assertion, are unmis¬ 
takable and indisputable, and the “ sore heels ” or “ grease ” he de¬ 
scribes as affecting horses and infecting the farriers who shod, or 
the grooms who attended to them, was nothing more or less than 
“ equine variola ” or “ horse-pox,” a disease which appears to have 
been far more frequent then than now, probably owing to the 
insanitary condition in which horses were kept in those days. 
Reference to his work* will show that Jenner knew more of the 
variolous diseases of animals than many more recent authorities, 
and that this “ sore heel ” disorder, or “ grease,” was eruptive in 
character, and could produce cow-pox. ‘Jenner’s discovery—for 
discovery this really was—was confirmed by Dr. Loy, of Pickering, 
wdio, in a little pamphlet which appears to be now quite unknown,! 
is even much more explicit than Jenner with regard to the nature 
of this inoculable “grease,” and he resorted to direct experimen¬ 
tation to prove the relations between it and cow-pox. His earlier 
experiments failed, in consequence of his not being able to dis- 
*“ An Inquiry into the Causes and Effects of the Variolae Vaccina, a disease 
discovered in some of the Western Counties of England, particularly Glouces 
tershire, and known by the name of cow-pox.” Loudon, 1798. 
t Account of some Experiments on the Origin of the Cow-pox. 1802, 
