ROBERT H. LISS AND JOHN C. NORMAN 
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alcohols and propylene oxide. Thereafter, the 
samples were embedded in Epon 812. Tissue 
sections were picked up on carbon-coated grids 
and stained with uranyl acetate and lead citrate. 
The sections were examined in an RCA EMU 
8G electron microscope. 
Other samples of lung tissue were prepared 
for scanning microscopy. After overnight fixa- 
tion in 3% glutaraldehyde millimeter cube sam- 
ples were rinsed thoroughly in several changes 
of distilled water. These were transferred to a 
glass slide and dried at room temperature over- 
night. Each sample was mounted on an individ- 
ual specimen holder and transferred to a vac- 
uum evaporator in which the samples were 
coated with gold. Thereafter the tissue was 
examined in a Cambridge Stereoscan Electron 
Microscope (Mark II). 
RESULTS 
Only animals in Group III showed clinical 
manifestations of pulmonary edema terminally 
and died after 5-6 hrs of infusion. 
Light Microscopy 
Scattered areas of induced pulmonary path- 
ology were observed in Group III dogs; i.e., 
continually overloaded with lactated Ringer's 
solution at 100 ml/kg/hr and without furo- 
semide treatment. Lung tissue from Group 
III dogs was edematous and congested. In 
Figure 2, interstitial edema, distended cap- 
illaries and intra-alveolar hemorrhage are 
seen. Ingestion of intra-alveolar erythrocytes 
by alveolar macrophages was observed ; the 
number of clear cytoplasmic vacuoles in these 
Figure 2. — Light photomicrograph of lung tissue from group III (continuously overloaded) dog. 
Interstitial edema (i), erj^hrocytes in alveolus (a) and crenated red blood cells (c) are seen. Note phagocytosis 
of red cell by macrophage (m) in alveolus (alv). x600. 
