INFLUENZA AND THE INFECTIOUS DISEASES OF THE HORSE. 261 
theories which seem most clearly defined and plausible, always 
present more or less obscure and debatable points. 
Brustseuche seems to have some analogy with the croupal 
pneumonia of the human subject. On this point Furgensen says: 
“ The portion of the pleura corresponding to the inflamed seg¬ 
ment of the lung is always altered. The injection of the blood 
vessels is first discovered in small sub-pleural ecchymoses; the 
serous surface becoming the seat of the trouble, thickening and 
becoming covered with false membranes, while effusion takes 
place in the chest. Thus, first localized in the pulmonary pleura, 
the inflammation spreads subsequently to the costal.” 
Fraentzel adds: ‘‘ The fibrinous pneumonia of man is always 
accompanied with pleurisy, even when the lesions of the lungs 
do not come in contact with the pleura, and these are ordinarily 
more affected in the costal than in the pulmonary region.” 
The result is that pneumonia is often only secondary, while 
pleurisy is the principal disease and may lead to death. The 
same observations may be made in brustseuche and in one of the 
other diseases. It must be acknowledged that the same causes, 
viz.: the same infectious germs, may give rise to both the pul¬ 
monary and costal lesions. 
The etiology of acute diseases, with a typical and regular 
course, of the organs contained in the chest is yet quite obscure. 
Siedamgrotsky has described : 
1st. Croupal pneumonia (lobar); 2d. Pleuresy (rheumatis- 
mal); 3d. Pleuro-pneutnonia (infectious pneumonia); 4th. Brust- 
senche, or contagious pleuro-pneumonia. 
This classification is based either upon the seat, the extent of 
the inflammatory groups of the diseased organs, or the degree of 
contagiousness of the affections. Without ignoring the practical 
importance it may possess from the point of view of the diagnosis 
of brustsenche, it must be acknowledged that it is difficult to dis¬ 
cern the difference that exists between the four divisions. 
The pneumonia that Siedamgrotsky and Roell have named 
croupal is not a sporadic disease affecting horses after exposure. 
It is, on the contrary, an infectious disease, with a typical and 
regular course, transmissible from one to all the occupants of a 
