R. A. GRIESEMER AND R. L. FARRELL 
955 
Figure 7. — Pneumonic consolidation (dark area) of 
nearly the entire apical lobe of the lung of a calf. 
dence of chronicity including adhesive pleuritis, 
abscessation, bronchiectasis, and organization. 
Fibrinous pneumonia presents a special prob- 
lem in the bovine. Pneumonic exudates from all 
causes in calves nearly always contain fibrin 
(Figure 9). In contrast with other species, bo- 
vine lung tissue contains little fibrinolytic activ- 
ity combined with large quantities of a protease 
inhibitor,^^'^* which result in delayed resolu- 
tion of the fibrin deposited after tissue injury. 
The usual outcome of fibrinous pneumonia in 
the bovine is organization and ultimate repair 
by fibrosis. Fibrinous exudate could conceivably 
decrease the alveolar surface area exposed to 
noxious agents and thereby result in differences 
in the response of the bovine lung to injury. An- 
other species variation of possible im.portance is 
that in the calf and sheep, eructation provides 
an opportunity for repeated inhalation of ru- 
menal gases. 
Calf Diptheria 
Calf diptheria is the common name for necro- 
tizing, pseudomembranous, ulcerative inflam- 
mation in the upper respiratory tract, caused by 
Fusiformis necrophorus. Lesions occur singly 
or multiply in the larynx, trachea, pharynx, or 
mouth. Typically, the lesions are well-demar- 
cated with central raised, roughened, adherent 
necrotic exudate (Figure 10) which sometimes 
sloughs leaving a circular ulcer that heals by fib- 
rosis. Overt clinical signs, when present, are 
persistent cough and occasionally dyspnea. 
While lesions of calf diptheria are no longer 
Figure 8. — Photomicrograph of pneumonic calf lung 
illustrating peribronchial accumulation of lymphoid 
cells. 
