Report on the Health of Animals of the Farm. 
277 
reported, also, that he had examined the lungs of an animal 
which had died of the disease in the same dairy. 
By what means pleuro-pneumonia gained a footing in England 
is not known, although it has been assigned to the importation 
of diseased animals from Ireland, into which country it has been 
asserted that it had been carried by some Dutch cows in 1839-40, 
which the British Consul in Holland had sent to Cork at the 
request of some of his friends. The difficulty in the way of this 
theory is, that the importation of animals into the British Islands 
was at that time strictly interdicted. Gaining a footing in 
England in 1841, the disease spread, but not so rapidly as to 
excite any great apprehensions in the public mind. Before the 
end of the year 1842, however, accounts had reached the Royal 
Veterinary College of cases having occurred in Essex, Cam- 
bridgeshire, Suffolk, Norfolk, Buckinghamshire, Leicestershire, 
Staffordshire, Lancashire, and Shropshire. 
In October, 1842, I had recourse to an experiment to deter- 
mine, if possible, the period of incubation of the disease, 
as the facts already ascertained by different observers as to the 
rate and the uncertainty of its progress among cattle with which 
diseased animals were herdecl were very discrepant. A cow 
suffering from pleuro-pneumonia was purchased, and brought 
upon the College premises, where she was put with a healthy 
cow which had been some time in my possession. The two 
animals were allowed to occupy the same shed for a few days, 
when the diseased cow died. In about three weeks from the 
time of the exposure, the experimental cow gave indications of 
being diseased. The symptoms of pleuro-pneumonia gradually 
developed themselves, and in seven or eight days from its com- 
mencement the case terminated fatally. 
The chief value, perhaps, attaching to this experiment is that 
of assisting to determine how early pleuro-pneumonia may be 
developed in an animal exposed to the disease by cohabitation ; 
for the length of time the morbific matter may lie dormant in the 
system has yet to be determined. Observations made on infected 
herds would seem to place this at the end of months, rather than 
weeks, and among numerous cases of this kind I may name one 
in which it was satisfactorily proved that the period could not 
possibly be less than ten weeks and three days. The solution 
of this one problem relating to pleuro-pneumonia can only be 
determined by a long series of experiments specially directed 
to it alone, and must, I conceive, be undertaken on a large scale 
and at considerable expense. The scientific investigator at once 
recognises the importance of a correct solution of the question, 
because he sees the error into which he might otherwise fall in 
