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PULMONARY MODELS 
Figure 1. — View of cat total lung block being anastomosed to left pulmonary hilus of a dog. The posterior wall 
of the cat's atrial cuff has been sutured to the dog's atrium and the transplant reflected posteriorly so that 
the atrial anastomosis can be completed, the pulmonary arteries anastomosed, and the cat trachea sutured to 
the end of the dog's left main bronchus. 
basic structure of the lung being observed. We 
are utilizing a metallurgical microscope with 
epi-objective lenses for m vivo study of the pul- 
monary vasculature during hyperacute rejec- 
tion.^ This microscope delivers incident light to 
the lung thereby eliminating the need for trans- 
illumination. We use this microscope to deliver 
the light in a dark-field mode which gives a side 
and back lighting effect, and a didymium filter 
which makes the erythrocytes highly visible. 
With this equipment we can record intravas- 
cular events on Kodachrome II film at film 
speeds up to 64 frames/second and 450 X 
magnification. The one factor that prevents 
such observation is a dense collagenous pleura. 
The cat and dog do not have such pleurae and 
are therefore highly suitable as well as readily 
available. Sheep have dense subpleural collagen 
and are not suitable, and pigs have a normal 
pulmonary pressure 15-20 mm Hg greater than 
the dog and are therefore unsuitable. 
RESULTS 
We have observed canine autografts, cross- 
sensitized canine allografts, and cat-to-dog 
xenografts successfully.- Of particular interest 
are the observations made in the cat-to-dog pul- 
monary xenografts. In this model, photography 
was begun with the cat lungs washed free of 
cells with cold, heparinized Ringer's lactate so- 
lution and transplanted, but before the dog's 
circulation to these lungs was established. When 
the vascular clamps were opened and flow be- 
gan, erythrocytes were immediately involved 
in dense aggregates. The aggregates appeared 
to form in the time required for passage from 
the dog's plumonary artery to the cat's alveolar 
capillaries i.e. in less than one minute. 
These erythrocyte aggregates did not adhere 
to the vascular walls but appear to jostle along 
in the vascular flow. However, they did adhere 
to each other and acted as large mechanical 
