2 MR. youatt’s veterinary lectures. 
^ung consists of three lobes, and the left of two; in the dog the 
right has five lobes and the left two, and these lobes are far more 
perfectly separated from each other than in the horse or the ox, 
for the separation commences even from the bronchial tubes. In 
the swine there are three lobes in the right side, or we may perhaps 
say that the right lung of the animal is divided into a great 
many lobes, for the smaller of the three is partially separated into 
numerous lobules, differing in number in different swine. The 
left lung consists of two lobes only, and the scissure between them 
is not very deep. The variations, then, have reference to the right 
lung—the left, in all our patients, has tw’o divisions only. The 
principal intention of these divisions is probably to adapt the 
substance of the lungs to the form of the cavity in which they are 
placed, and to enable them more perfectly to occupy and fill the 
thorax. 
The external Form of the Langs .—The lungs are suspended 
from the spine by means of their bloodvessels, the bifurcation of 
the bronchise, and the mediastinum. Their fiorure is irregular, 
elongated, flattened, pyramidical; broad and concave posteriorly 
where they are in contact with the convex surface of the diaphragm; 
and narrow'er, and approaching to a point anteriorly, where the 
cavity of the thorax narrows. W e recognize in each three surfaces, 
the costal, the diaphragmatic, and the mediastinal. The con¬ 
vexity of the costal accommodates itself to the concavity of the 
ribs; the concavity of the diaphragmatic surface answers to the 
convexity of the diaphragm, and the mediastinum adapts itself 
to the irregular surface to wdiich it is exposed. The rounded 
borders, superiorly, fill the longitudinal cavity or sulcus on each 
side of the dorsal vertebrae; the narrower borders inferiorly bend 
towards each other, and enclose the apex of the heart; the poste¬ 
rior borders follow the curvature of the diaphragm, and constitute 
the base of the lungs. The lungs are enveloped, as I have already 
described, by duplicatures of the pleurae. 
The internal Structure .—We cut into one of the lobes, and 
we find it separated into numerous irregularly-formed compart¬ 
ments, to which anatomists have given the name of lobules or little 
lobes. They are separated from each other by cellular membrane. 
They are distinct from each other; and they are impervious, 
except through the medium of the air-tubes and bloodvessels 
which pass into and through them. We examine them more 
closely, and we can subdivide them, and almost without end : 
•we have smaller lobuli, each surrounded by cellular membrane, 
each distinct from and having no communication with its fellows. 
The consideration of some of the diseases of the lungs, and particu¬ 
larly broken windy will convince us of the independence of, or 
