27 
are normally present at this point. The alveolar spaces 
mentioned above are lined with cells that bear a great re- 
semblance to glandular cells, but are also somewhat like 
the low columnar type of the terminal bronchioles. The 
smaller bronchioles in the immediate neighborhood of this 
distended one are quite irregular in shape; the mucosa, 
however, seems properly restrained by its basement mem- 
brane, and at no point can a distinct breaking through be 
discovered. Moreover, the cells of the small nests resemble 
more the glandular epithelium, and if these have originated 
from a bronchus, a metaplasia has occurred. Although the 
bronchioles are very irregular in their size and shape, there 
are no. solid plugs of cells extending into the surrounding 
tissue as in the case of the tumor in the civet's lung. In- 
asmuch as it is improbable that a carcinoma arising from 
a bronchial wall would develop nests in a fibrous stroma 
without passing through some of the stages of an epithelioma 
and at the same time do so without leaving a trace in our 
sections (assuming that this occurred in the section of two 
millimeters which is missing), a carcinoma arising from the 
bronchial mucosa does not seem to be a diagnosis against 
which no objection can be raised. Again, the glands were 
normal proximally to this new growth, while no typical 
adenomatous structure can be found in or about it. There- 
fore, they must have ceased somewhere withhi the missing 
two millimeters, and at the point of their normal disap- 
pearance may have continued to develop in an atypical 
manner, extending along the fibrous sheath of the bronchiole, 
their extramembranous nests using the lymph channels as 
routes of extension. The alveolar epithelium must not be 
overlooked, but inasmuch as a large part of the atypical 
acini are outside the connective tissue adventitia of the 
bronchiole, the masses in the alveoli must be in a great 
measure secondary. The excessive amount of connective 
tissue around this neoplastic process is suggestive of a me- 
tastatic growth. There was no other growth in the animal's 
body from which to have metastasis. 
While the exact origin of this tumor cannot be asserted, 
its most probable starting point appears to be the glands 
