7 8 E VOL UTION AND DISEASE. 



organ to indicate its previous existence. A careful 

 inquiry will reveal the occasional presence in the 

 tongue of a duct passing from the hyoid bone to the 

 foramen caecum. This is not a duct which requires a 

 microscope to distinguish it, but is capable of admitting 

 a bristle or fine probe. In some cases this duct becomes 

 obstructed at the upper opening, and the gradual accu- 

 mulation in its interior of shed epithelium and sebace- 

 ous matter gradually distends into a large and trouble- 

 some cyst. In some cases the walls of the cyst are 

 formed of skin, and hair may sprout from it. These 

 cysts are not infrequent in the human subject, and have 

 been found occupying the centre of an ox tongue, under 

 rather unpleasant circumstances. A gentleman, whilst 

 carving a tongue at breakfast, unexpectedly came upon 

 a collection of hairs and fatty material in its midst, and 

 was in no small measure astonished. 



The mammalian tongue should be an organ of great 

 interest to the morphologist ; unfortunately ks evolu- 

 tion has not yet been thoroughly unravelled. It has 

 of course received great attention from anatomists and 

 surgeons. From anatomical and pathological stand- 

 points the anterior two-thirds of the tongue differ com- 

 pletely from the posterior third. The latter part may 

 be regarded as the more primitive, whilst the tip of the 

 tongue is of later development and, morphologically, 

 less important. 



