TRANSLATIONS FROM CONTINENTAL JOURNALS. 175 
is well known. He adopted the whole of the tradition, 
except the origin of the cow-pox, which tradition made to 
originate ‘ with the cow. Jenner, however, made its origin 
to be from the horse. Nothing is clearer and more explicit 
in this respect than his words. We have not the English 
text under our eye, but here is the Latin translation by Carro 
(Vienna, 1799) :—Planta pedis inflammata tumet, unde 
materia peculiaris indalis profluit quie in corpore humano 
morbum variolis ita similem exitat ut plane non dubitem 
variolas ipsas ab hac materia originem traxisse.^^ The same 
observation might certainly be made as to the correctness of 
this translation of the text, if it be a correct one; as, for 
instance, it states that the seat of the disease is at the bottom 
of the foot: but let this pass. On the origin of the vaccine, 
Jenner, for certainty, never varies in opinion. In the state 
of domesticity in which the horse is kept, he says, it is sub¬ 
ject to a malady similar to variola, and which must arise from 
the same source. Afterwards he adds, If you meet with 
the cow-pox in a number of cows, you may be sure that it 
has been produced by men who had been dressing horses 
that were affected with grease.^^ Qui prius equarum ulcera 
ad ungulas affectorum tractaverunt.^^ At one time Jenner be¬ 
lieved that, to obtain perfect immunity from variola, the matter 
of grease must go through the cow; but afterwards he 
declared that this was not necessary, from which it appeared 
that as he advanced in life he became more confirmed in his 
genealogy of the cow-pox. But Jenner was well aware that 
the question was one of observation rather than experi¬ 
ment. Unfortunately, he made but one experiment, and that, 
most unfortunately, was a failure, for it proved more against 
him than for him. Nevertheless that did not prevent him 
carrying the conviction to the grave that the cow-pox 
originated primarily and spontaneously in the heels of the 
horse, from which it passed by contagion to the cow. 
Observation may quietly await the solution of the problem 
of these fortuitous inoculations, if sometimes they do take 
place; but observation is often fallacious —Experientia fallax. 
Experimentation, less patient, goes to meet the object it 
wishes to know; it tries to create artificially the cow-pox, by 
transmitting the virus from the heels of the horse to the cow 
or to the human subject. Sure of the process, it is sure of 
the result. Unfortunately, in physiological questions experi¬ 
mentation does not always hold the same language, and is 
often silent. Hundreds have transferred the virus of grease 
from the horse, and it has given the cow-pox to some and 
not to others. It has given it to Lay, to Carro, his Latin and 
