as observed in the Tongue of the living Frog, Toad, fyc. 277 



oodies of irregular curved outlines, which may be considered 

 as the second anatomical stratum of the tongue ; these con- 

 sist of papillae, small glands and mucous follicles. 



The papillae are small bodies of a cylindrical, conical or 

 club-like shape, connected at the base so as to be continuous 

 throughout. In thickness or breadth they vary between about 

 m, 25 and m 05: their length cannot be accurately deter- 

 mined, as they have no fixed line of demarcation at their point 

 of insertion on the mucous membrane. No appearance of any 

 circulation is found in any of these papilla? : the blood-vessels 

 run by them, sometimes forming vascular loops, but are 

 rarely seen to penetrate through them ; and even in those 

 cases the vessel is frequently external to the papilla, which is 

 sufficiently transparent to allow the blood-vessel to be seen 

 through it. In inspecting the surface of the tongue, espe- 

 cially when the high powers are used, a mistake may be 

 easily made, against which I wish to guard those who may 

 repeat these experiments : it consists in the appearance of 

 numerous curved lines running in every direction, perfectly 

 black, and apparently very defined. These lines have been 

 supposed to be loops of nervous fibres ; and M. Donne ap- 

 pears still to labour under that erroneous idea, when at page 

 116, Cours de Microscopic, he says, " d'autres taches grises se 



remarquent Je les crois formees par des houppes ner- 



veuses." These lines are nothing more than the outlines of 

 the papilla of fig. 1, seen not exactly at the right focus. 



From the nature of their structure and functions we should 

 expect to find some nervous filaments in the interior of the 

 papillae ; and probably such do exist, though I have not yet 

 been able to detect them. The nervous fibres, which are 

 found below this layer, will be examined hereafter. They 

 never present any opening ; the dark points sometimes seen 

 at their apex belong to some central spots of the epithelial 

 scales, with which they are covered as with a glove ; nor do 

 they ever appear flaccid or empty. 



Glands *. — The glands of the frog's tongue differ from the 

 papillae by the very active circulation which they present in 

 their interior. They are always of a globular shape, more 

 prominent and larger on the surface than the papillae, being 

 generally about the j^q^ 1 °f an inc ^> The circulation in 

 these small glands is very interesting to witness, as we can 

 trace the progress of the particles of the blood as they enter 

 into the centre of the gland, and follow them in all their move- 

 ments, until they make their exit in the capillary vessel which 



* These will be shown hereafter to resemble the fungiform papillae in 

 the human subject. 



