IRS - The Philippine Journal of Science 1915 
enhanced when it is learned that the pulmonary changes spoken 
of are of both origins—as infarcts and as metastases. 
HISTOPATHOLOGY OF THE LUNGS 
_ In the first or purely bronchopneumonic type of lesion the 
microscopic changes do not: differ essentially from the same 
lesions caused by other organisms. Surrounding the bronchi 
there occur localized areas in which the alveoli contain some 
serum, many red blood cells, a few leucocytes, and some large 
pigment cells. The capillaries in the alveolar walls are engorged, 
and small hemorrhages may occur. The tissue immediately 
surrounding the consolidated area is congested and may show 
some collapsed alveoli. The bronchi show evidence of a simple 
catarrhal inflammation. Bacilli are, as a rule, not a prominent 
feature in sections of lungs of this type. Fibrin in the exudate 
is very scant or completely lacking. 
In lesions of the second and third types (peripheral infarcts 
and metastatic embolic pneumonia) the leucocytes and bacteria 
are present in greater abundance, and the destruction of tissue 
is greater than in the first type. Here one finds foci of very 
dense infiltration with polymorphonuclear leucocytes and a few 
erythrocytes. These are enmeshed in a fine fibrillar network. 
Weigert’s stain for fibrin shows some fine strands and networks 
of fibrin, but this is not nearly so abundant as in a frank lobar 
pneumonia. In the alveoli are also seen many large pigmented 
cells, obviously desquamated epithelial cells from the alveolar 
wall. These cells are found very constantly in the pulmonary 
alveoli in plague, irrespectively of whether or not there is con- 
solidation present. Bacilli may be present in some of the alveoli 
in rather large numbers, but in this series they are not nearly 
so abundant nor so conspicuous a feature as they were in a 
previous series of primary pneumonic-plague cases. Nuclear 
fragments may also be abundant in the alveoli. 
In the central parts of the nodules the interalveolar septa are 
represented by diffuse eosin-staining masses, which show no 
organized structure. In the places of some of these are dense 
masses of bacilli, which masses have such shapes as to suggest 
that they lie in vessels, although all traces of the vessels have 
disappeared. The peripheral parts of these foci show better 
preserved septa, with engorged capillaries; the septa, however, 
show the same type of changes as described in the smaller splenic 
vessels. They are thickened and more or less homogeneous, 
take the acid stains, and show a fibrillation of their structure. 
Over the peripherally placed infarcts there is a delicate layer 
