TISSUES OF THE BODY. 



151 



Fig. 148. Gob let-cells from the epi- 

 thelium of an intestinal villus from 

 the hnman subject,' treated with 

 Mailer's fluid (Schutze). a, goblet- 

 cells; &, cylinder-cells. 



in the form of a cylinder, less frequently as a more rounded or flattened 

 body. The undeveloped elements, lying deeper down in the tissue spoken 

 of as laminated ciliary epithelium, are 

 rounder, and destitute naturally of the char- 

 acteristic cilia. 



The columnar cells of ciliated epithelium 

 (fig. 149) manifest the same diversity of 

 form, and the same difference of length, as 

 those of the simple tissue. The free edge of 

 the cell sometimes presents a darker con- 

 tour than the side Avails. Its substance is 

 at one time transparent, at another, finely 

 granular, but always tolerably pale. The 

 number of cilia, as we have already mentioned, is liable to vary, and ranges, 

 probably, between ten and thirty. In mammalian animals and man 

 the cilia appear somewhat flattened, and terminate above slightly blunted, 

 although some observers speak of their being pointed. The size of these 

 minute hairs is subject to variation among the higher animals. In the 

 first place, those attached to any one cell are not 

 necessarily all of the same length ; and again they 

 are met with of larger or smaller proportions in 

 different localities. The gigantic magnitude which 

 they attain in many of the lower groups of animals 

 is never seen here. The largest cilia, of from 

 0-0226 to 0-0340 mm., are found in the human 

 subject upon very large -sized cylinders, mea- 

 suring '0445-0 -0560 mm., which clothe the 

 upper part of the passage of the epididymis 

 (Kolliker). 



In other situations the cilia are smaller, as for 

 instance in the com vasculosi of the testicle (0'0114 mm.), but their length 

 is still less in the epithelial cells of the respiratory organs, namely, 

 0-0056-0-0038 mm. The length of the cells themselves ranges in the 

 human body from 0-0285 to 0"0570 mm. The cilia are of a delicate and 

 perishable nature, and consequently decay rapidly a few hours after 

 death. At times, however, they remain exceptionally in a very perfect 

 condition even for days in the bodies of the warm-blooded animals. 



Ciliated epithelium is found in the following parts of the human 

 body : 



It clothes the mucous membrane of the respiratory tract, commencing 

 at the base of the epiglottis, after which it covers the whole larynx, with 

 the exception of the vocal chords. Here it is slightly laminated, forming 

 a bed of from 0*0056 to 0*0992 mm. in depth. It likewise extends over 

 the trachea and bronchi with decreasing lamination, until at last the 

 very smallest tubes are covered with a single layer of minute elongated 

 ciliated cells, 0-0135 mm. high (Koelliker). 



The organs of smell also possess a laminated ciliated epithelium, com- 

 mencing about at that point at which the cartilaginous nose terminates. 

 It is from 0*0451 to 0-0992 mm. in thickness. The regio olfadoria alone, 

 in the more restricted application of the term, is an exception to this 

 with its epithelium, which will be considered more at length in discussing 

 the apparatus. Moreover, it is not only the main cavities which are lined 

 with these cells, but the adjacent ones also connected with the organ. 

 11 



V 



#. 149. Ciliated cells from 

 the mammal, a b, simple 

 forms; c, narrow elongated 

 cell; d, one still more so, 

 with double nucleus. 



