256 THE AMEEICAN MONTHLY [November, 



The Epithelium of the Brain Cavities. 



By PIERRE A. FISH, 



ITHACA, N. Y. 



The contradictory statements of various autliors as to the existence 

 of ciliated epithelial cells in the membrane lining the brain cavities, 

 has been one of the chief reasons for pursuing this investigation. 



For the practical purposes of this study the cat was chosen, because 

 it is easily accessible and is a good representative of the class mam- 

 malia ; furthermore, in the opinion of the writer, the morphological 

 differences of these epithelial cells, in mammals generally, are less 

 important than their resemblances. Special attention was given to the 

 diaccele, mesocade, and epico^le. Three stages were studied : at birth, at 

 six weeks, and adult. Ciliated cells were found in all which resembled 

 each other so closely in structure that the stages might easily be inter- 

 changed. For details high powers should be used ; nothing less than 

 600 diameters will give satisfactory results. 



Preparations hardened by Goule's method show the cilia quite well either 

 when sectioned or after being teased. The epithelium in some places 

 may be stripped from the adjacent tissue as a continuous membrane, 

 and this, after remaining for a short time in some dissociating agent, may 

 easily be teased apart. 



The cells are very short, columnar in outline, and ciliated at their 

 free ends, the long diameter of a cell including the cilia being 9;/. 

 The cilia are relatively much longer than usual ; they represent about 

 one-fourth of the entire length, or 2.5//.. In hardened preparations they 

 are not always perfectly preserved, often appearing to have been thinned 

 out and broken ot?'. A thorough injection of the hardening agent into 

 the cavities will do much toward obviating this undesirable feature. 



The nuclei, more or less oval in outline, nearly fill up the cell bodies. 

 In none of the nuclei, stained or unstained, could nucleoli be detected, 

 although numerous clear spots could be seen, particularly in the fresh 

 specimens. 



The cell-bodies send offone or more roots into the adjacent tissue and b}' 

 means of them are anchored to their places. The neuroglia varies in 

 thickness at different places : under a high power it has a wavy, 

 homogeneous, and slightly fibrous appearance in which are scattered 

 neuroglia cells. It passes imperceptibly into the true nervous substance 

 as a connective medium, binding together nerve cells and fibres. 



The propulsion of the cerebro-spinal fluid through the cavities, if 

 cilia are absent, may be accounted for by the brain movements stimulated 

 by psychical, circulatory, and respiratorv influences. In the embryonic 

 stage where these influences are, not yet or only about to be, developed, 

 cilia abound. 



This investigation has demonstrated the existence of ciliated epithe- 

 lium in the endyma (lining membrane) of the adult as well as earlier 

 stages of the cat. 



If psychical phenomena are not incompatible with the presence of 

 endymal cilia and if the brain is treated while perfectly fresh, there 

 seems to be no good reason, from a morphological stand-point, why cilia 

 should not likewise exist in the endvma of the human adult. 



