NEW RESEARCHES UPON PLEURO- PNEUMONIA, ETC. 417 
ply, and thus transmits the contagion from the east towards the 
west, as we have seen, some years ago, a sad example at Hasselt; 
in the same manner pleuro-pneumonia is spread in an inverse 
direction; it travels from the centre of Europe towards northern 
and more rarely towards oriental countries, where it is always 
transported from the west. Once introduced in a country, it 
makes it its home and cannot be extripated except by the most 
rigorous hygienic measures; it is propagated by contagion from 
one animal to another, from one stable to another, and that 
especially in countries where the trade in cattle is very active, and 
where administrative and sanitary measures are less rigoiously 
observed. 
In a stable or in a herd, the contagious principle is spread over 
all the animals in the same way as the sun and light are. They 
have not all the same receptivity. Tins is why I have often 
seen the animals most distant from the affected subject afflicted 
first, and those which were nearest to him later. The disease may 
also be transmitted from one stable to another through the medium 
of the air loaded with the contagion ; the transmission can also 
take place at long distances, as observed by some. This fact was 
confirmed by the experiments of the French Scientific Commis¬ 
sion and by a very curious observation of Mr. Sluys, of Bernesters, 
reported in the Landbouw Courant of April 14th, 1870. 
C. Contagion has been rigorously demonstrated, and spon¬ 
taneity has not as yet. In favor of the last, there are only prob¬ 
abilities so far; the disease has never been created by the means 
of determined circumstances. Any attempt made to produce it 
spontaneously has failed, and the diverse circumstances in which 
animals were placed while under experiments, have only produced 
in them a greater disposition to become contaminated and to a 
shorter period of development. 
All imaginary causes, so invoked by the spontaneites, such as 
bad stabulation, warm and damp and bad stables, too rich and ex¬ 
citing feeding, residuum of sugar houses or of distilleries, expos¬ 
ure to cold and damp air, too abundant secretion of milk, exces¬ 
sive work in oxen, &c.—all these causes, single or collected, have 
never given rise to a case of pleuro-pneumonia. 
