The structure of the distal border of the olfactory epithelium from 25 normal adult dogs of various breeds was studied with the electron microscope. Sections of vesicles of olfactory cells were found to contain 6-16 characteristic cilia; it is estimated that a total of 100-150 olfactory cilia are probably present on each cell. The basal corpuscles of the cilia contained two accessory structures, namely the basal feet and the cross-striated rootlet fibers. The rootlet fibers consisted of a striated bundle of several fine, closely adherent filaments. Microtubules and multivesicular bodies were found in the olfactory cells. The supporting cells were easily recognized by their unique bushy microvilli, electron opaque cytoplasmic organelles, and smaller-sized multivesicular bodies. In addition to the usual supporting cell type, an apparent fourth cell type was observed. It contained short, sparse microvilli. This cell type was easily identifiable by the presence of a more electron translucent cytoplasm, and was postulated to be a precursor of the usual supporting cell type.
Bibliographical noteFunding Information:
Since the classical studies on the olfactory epithelium conducted by Schultze (27) and Eckhard (11), many papers have been published on this subject. In 1927, Kollmer (15) reviewed the literature up to that time. Electron microscopic studies have revealed many additional cellular structures which the light microscope could not demonstrate. Bloom (1), and Bloom and Engstrom (3) were the first to use the electron microscope for studies of the olfactory epithelium. In later studies Engstrom and Bloom (12) published detailed descriptions of the structure of the olfactory region in z Approved for publication as Scientific Journal Series Paper No. 5867, Minnesota Agricultural Experiment Station. This investigation was supported in part by U.S.P.H.S. Research grant No. GM-07009. Present address: Laboratory of Animal Anatomy, College of Agriculture and Veterinary Medicine, Nihon University, Shimouma, Setagaya, Tokyo, Japan. Present address: Department of Veterinary Anatomy, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota.