rats 20,800µm^2: human 206,900 µm^2 µm^2
||Stone KC, Mercer RR, Gehr P, Stockstill B, Crapo JD. Allometric relationships of cell numbers and size in the mammalian lung. Am J Respir Cell Mol Biol. 1992 Feb6(2):235-43 DOI: 10.1165/ajrcmb/6.2.235 abstractPubMed ID1540387
||Abstract: "The average alveolus in the inflation-fixed lungs of the rats [investigators] studied had a surface area of 20,800 µm^2 and was covered by only four type I and six type II cells. In contrast, the average human alveolus had a surface area of 206,900 µm^2 and was covered by 40 type I and 67 type II cells. These data support the hypothesis that cell size and surface area are determined by cell function and not by species size."