EPITHELIUM. 241 



influence ; acetic and the mineral acids destroy the motion, as 

 also caustic ammonia, nitrates of potash and of silver. The 

 serum of the blood prolongs its duration. Urine and white of 

 egg are without effect upon it. Bile instantly destroys the 

 activity of the ciliae. 



The ciliary motion soon ceases after death in the mammalia, 

 but continues in many of the invertebrata, and especially in 

 several of the mollusca, as for example, in the river muscle 

 and the oyster, for days after the death of the animal. 



It would appear, therefore, that each ciliated corpuscle 

 bears the closest possible resemblance to many of the infusory 

 animalcules, and it is questionable whether its claim to be 

 regarded as a distinct entity be not equally strong. 



Distribution. Ciliated epithelium has not been as yet dis- 

 covered amongst the mammalia in any closed cavity, but 

 always in situations which communicate with the air ; thus 

 it is met with, as is generally known, lining the trachea and 

 bronchi, extending even to their minutest ramifications ; again, 

 it is encountered in the fallopian tubes, and lining the upper 

 third of the cavity of the uterus of adult animals, but not 

 that of young mammalia. There is yet another locality in 

 which I believe it also to exist, viz. in the convolutions of 

 the tubuli seminiferi of the epididymis. 



On the other hand, there are many situations in which it 

 has been repeatedly asserted to exist, but in which patient 

 and repeated investigation has failed to reveal its presence, as 

 for example, in the ventricles of the brain *, covering the pia 

 mater, and lining the eyelids and frontal sinuses, f 



The epithelium of these several parts, on the contrary, is 

 pavement and not ciliated epithelium. (See Plate XXIV.) 



Purkinje J, in describing the epithelium of the ventricles, 

 does so most circumstantially, and states that he followed the 

 vibratile movement in the sheep from the lateral ventricles 

 through the third ventricle, and by the aqueduct of Sylvius 

 into the fourth. 



* Purkinje in Muller, Archiv. 1836, p. 289. 



f Henle, Anat. Gen. t. vi. p. 252. J Muller, Archiv. 1836. 



