284' Dr. Waller's Microscopic Examination of the 



tleslroying the papillary surface of the organ; and also he com- 

 mits the mistake of regarding the papillae as glandular bodies, 

 as we may see by the following passages. " There are con- 

 siderable difficulties, even in the frog, in recognizing the course 

 of the nerves in the interior of the tongue ; for independently 

 of the thick layer of mucus secreted on its surface, this organ 

 is obscured by a multitude of granules or opake knots, globular 

 in form, which are doubtless mucous glands ; and likewise by 

 numerous canals, variously twisted, of a thickness nearly equal 

 to j^ijth of a line, which appear to be filled with corpuscles re- 

 sembling the blood-discs, and which are either canals to convey 

 the mucus, or lymphatic vessels ; and lastly by numerous blood- 

 vessels. Therefore we soon become convinced of the impossi- 

 bility of distinguishing anything without the employment of 

 artificial means An impossibility already ex- 

 perienced by Valentin and which my own researches have con- 

 firmed All chemical substances, whatever they 



may be, when applied during the life of the animal on the sur- 

 face of the tongue, have always produced an increase in the 

 afflux of the blood to the organ, and have still more injured its 

 transparency*." 



In order to detect the real extremities of these nervous fila- 

 ments, we have but to examine with care the papillary surface 

 of the frog's tongue. If this is well extended and not over-in- 

 jected with stagnant blood, we shall have no difficulty in dis- 

 cerning, at the base of each fungiform papilla, a dark gray 

 spot formed by a nerve nearly the size of a capillary vessel. 

 In fig. 1 we have a very correct repi'esentation of a papilla as 

 it appears in a favourable subject. The nerve, of which we 

 see a portion, pursues a very winding course. Near the base 

 of the pedicel of the papilla it is usually twisted, as is repre- 

 sented, into a kind of loose knot composed of several loops. 

 This spot is the darkest portion of the nerve, and is to be seen 

 in most of the fungiform papillae. From this point the fibres 

 ascend apparently less numerous, and accompany the blood- 

 vessels in their numerous gyrations within the papilla. By 

 reason of the darkness and opacity of the Llood-vessels the 

 numerous convolutions are generally concealed, and it is only 

 at the intervals between the coils that we are enabled to detect 

 the nervous tubes. The principal varieties which I have had 

 occasion to remark with respect to these papillary nerves, are 

 that sometimes the efferent and afferent capillaries run close 

 together joined to the nerves, which in that case are in a great 

 measure concealed. Sometimes thenerve, like the blood-vessels, 



* Burdach, Structure des Nerfs, — Annales des Sciences Naturelles, vol. ix. 

 2i4me series. 



