6 1 
structure of the cells of the human lungs , &c. 
the pulmonary artery, injected with red wax, were seen 
ramifying, as arteries do in common ; these were accompanied 
by branches of the pulmonary vein, larger in proportion than 
those of the arteries, more numerous, and having valves, at 
apparently regular intervals, to prevent regurgitation of their 
contents. Besides the arteries and veins, there were innu- 
merable absorbents opening into the cavity of the cell ; their 
valves were at very short distances, and, in their course in 
the interstitial substance between the cells, they accompanied 
the veins. When the terminal branches of the pulmonary 
artery were traced, the injection was found to have stopped 
someway before the artery’s termination, and the space 
beyond was filled with gas. The substance of the lungs, 
interstitial to the cells, when dried became transparent, and 
w r as found to be composed of a smaller order of cells, with 
transparent coverings, that freely communicated with one 
another, as well as with the cavity of the large cell they 
surrounded. 
I cannot finish this description of an internal view of one 
of the cells of the human lungs, without expressing the obli- 
gations I am under to Mr. Dollond, who from a zeal for 
science, and the peculiar interest he has taken in these phy- 
siological enquiries, has fitted up the microscope (from the 
field of which the representations were taken), possessed 
of advantages beyond all the others that Mr. Bauer has met 
with, not excepting the achromatic microscope, as improved 
by Mr. Chevalier of Paris. This of Mr. Dollond, from the 
superiority in the clearness of the different glasses, and the 
facilities which are given to the variations of the nicer adjust- 
ments of the instrument, has enabled Mr. Bauer to give a 
