STUDIES ON CILIATED CELLS 229 



formed into ciliated cells. This is a physiological change which 

 is going on, not only in embryonic or 3^oung tissues, but also in 

 those which are fully developed. Under these conditions, the 

 differentiation of the superficial plasma-portion of a ciliated cell 

 might be considered from two morphological points of view: 

 first, from the structures derived from the normal columnar 

 cell, and then from what are newly formed with the develop- 

 ment of the ciliary apparatus; and it is natural that these differ- 

 entiations vary according to the forms of epithelial tissues in 

 which the ciliated cells are involved. 



It is extremely rare that the ciliated cell exhibits no special 

 differentiation in its distal border. Even in such cases as where 

 a distinct cuticle seems to be lacking, as Lenhossek ('98) and 

 Studnicka ('99, '00) state, the distal border of the ciliated cell 

 where the basal corpuscles lie, is somewhat dense in character 

 and stains more heavily with plasma-dyes. This fact might 

 have, as Lenhossek remarks, a certain amount of importance for 

 the physiological function of the cilia. 



1. Relation between the cilia and the cuticle. Friedreich ('58) 

 was the first to describe the cuticular border of the ciliated cell ; 

 he found a striated cuticle in the ciliated cells of the trachea 

 of man and bull, and of the ventricular wall of the human 

 brain; and believed that the cilia pass into the cytoplasm along 

 the striae. The structure in question has since been noticed by 

 Eberth ('66), Marchi ('66), Engelmann ('68) and others. 



I find in the literature of the subject five different opinions 

 with regard to the structure of the cuticular border and the 

 manner of implantation of the cilia: 



1) Rabl-Riickhard ('68) asserts that, although he found a 

 cuticle in the ciliated cells of gills of Annelida, the cilia never 

 pass through it, but are attached to its upper surface by some- 

 what dilated bases. 



2) Friedreich ('58), Stuart (67), Apathy ('97) and Gurwitsch 

 ('01, '04) believe that the ciliated cell has a homogeneous cuticle, 

 through which the cilia pass into the cytoplasm, and, in addi- 

 tion, it was shown by Gurmtsch that the cuticle must be soft, 

 since the cilia pass through it irregularly. 



