25 
TWO INSTANCES OF PRIMARY CARCINOMA OF 
THE LUNG IN ANIMALS. 
The two examples of primary carcinoma of the lung here 
reported were observed by accident, while posting a wool- 
less sheep and a civet, that from the former having been 
mistaken for another condition, while that from the latter 
was found only by microscopic examination. The value of 
these cases lies in the fact that primary carcinoma of the 
lung in human beings is rarely seen at a stage early enough 
to determine the exact origin of the epithehal cells forming 
the nests. The metaplasia which these cells undergo, after 
leaving their normal arrangement, renders it difficult to 
determine their origin with absolute certainty when the 
tumor has reached the extent commonly seen in such growths 
of the human lung. 
Indeed, it is not possible to determine the origin of the 
tumor in the sheep's lung, without question, inasmuch as 
a mistake in primary diagnosis at autopsy was responsible 
for cutting the section so as to lose a shce about two milli- 
meters thick, just to the proximal side of the neoplasm. 
This will be described further on. 
Cancer of the lung is frequently preceded or accompanied 
by some disturbance in the lumen of the bronchus, the most 
frequent change being bronchiectasis. Tuberculous cavities 
and bronchi obstructed by phthisical processes seem to be 
especially prone to malignant degeneration of their walls. 
Here, however, epitheUoma with pearl formation is most 
often reported. In one of the cases (sheep) the neoplastic 
process is occurring around a bronchiectasis of non-tuber- 
culous nature, but the development of the tumor sprouts 
and cell nests is typical of carcinoma. The absence of pearls 
in the tumor masses, situated as they are in a scirrhus stroma, 
distinctly favors the determination of carcinoma. The- cel- 
lular elements predominate in the tumor of the civet's lung. 
