164 DISEASE IN WILD MAMMALS AND BIRDS 
should carry away infection one would think. Perhaps 
this high percentage of pleurisy in our Pinnipedia is but 
accidental. The marsupials, while having a notable per- 
centage of pleurisy both among all the cases and in rela- 
tion to the number of postmortems, are not so striking 
from the etiological standpoint since practically all of 
these have suffered with Kangaroo mycosis or pneumonia. 
In over half the cases of this infectious disease some grade 
of pleuritic exudate has been observed, only one, however, 
going to the stage of empyema. 
One cannot speak so definitely of pleuritis in birds 
since this tissue merely represents in them the covering 
of the lung and is firmly attached posteriorly to the ribs 
and anteriorly to the air sacs. Exudates show as col- 
lections upon the air sac side of the combined membrane, 
pleuritis proper in birds being an infiltrative affair com- 
ing through the pulmonary tissue and therefore being a 
part of pneumonitis. I notice a tendency in a few articles 
to write of pleuritis when the process is confined to the 
thorax but this gives the impression that the disease is 
peculiar. There seems no difference in the gross and 
minute appearance between thoracic serositis and pan- 
serositis. The course of procedure seems to be from the 
anterior or mesial pulmonary ostia into respectively the 
cervical and thoracic air sacs and this seems to hold good 
whether the infection be mycosis or fowl cholera or fowl 
pest. There are records of 104 cases of serositis in birds 
of which 45 were among parrots, the remainder being 
well distributed among the various orders ; only two each 
occurred in Galli and Anseres, orders prominently 
affected under domestication. This high percentage of 
pleuroperitonitis among parrots and their congeners can 
only be explained upon the ground of a continued infec- 
tion of our stock by the virus of fowl cholera and by 
mould. One case of undoubted fowl cholera occurred 
recently and as the records are reviewed a few are dis- 
covered where the organism was found. The virus must 
