C 301 3 
XXI. On the effects produced upon the Air Cells of the Lungs 
when the pulmonary circulation is too much encreased. By 
Sir Everard Home, Bart. V.P. R. S. 
Read May 31, 1827. 
While Mr. Bauer was engaged in making the microsco- 
pical observations contained in a former paper on the struc- 
ture of the human lungs, he compared the appearances with 
those in the lungs of other animals, and found in the quadru- 
ped the principal difference to be, the more minute branches 
of the bronchia? have imperfect cartilaginous rings to a greater 
extent towards the air cells than in the human lungs. 
In cold blooded animals, as the turtle, the bronchia? do not 
in their ramifications diminish as in the quadruped, but remain 
of a considerable size, and the lateral branches degenerate 
into a trellis work, which is only bounded by the circum- 
ference of the organ. 
The cells of the human lungs are not dilatations of the 
bronchial tubes, but are regular cells in which the tubes ter- 
minate. The animals Mr. Bauer examined were the hare, 
the sheep and the turtle. In the human lungs and those of 
the hare the superficial cells are larger than the interior. In 
examining the air cells of a hare that had been coursed, he 
found the superficial large cells filled with colourless coagu- 
lable lymph, forming white specks, and the smaller more 
interior ones filled with coagula of red blood. No such ap- 
pearance was met with in a hare that had been snared, or one 
that had been shot. 
