448 INNERVATION. [CHAP. XV. 



many substances is, however, very different from that which they 

 produce in the first instance. Horn has remarked that this after- 

 taste is usually bitter ; while, with one of the most bitter substances 

 known, viz., tannin, it is sweet. This circumstance appears to shew 

 something in taste corresponding to the complementary colours in 

 vision, and seems dependent on a state of the nerves which, for want 

 of a better word, may be termed one of exhaustion, consequent on 

 their previous stimulation. It will illustrate the cause of many fami- 

 liar phenomena of taste ; such as the effect some flavours have in ex- 

 alting, modifying, or destroying our appreciation of others. Repeated 

 over- stimulation of the nerves by the same substance exhausts their 

 excitability by that or similar substances for some time afterwards. 



There also appear to be relations between certain varieties of 

 taste, which, though not classified or described by philosophers, are 

 instinctively perceived, and constitute the foundation of the art of 

 cookery. Attention and study given to the perceptions of this sense 

 greatly enhance their delicacy. 



Little is known of the subjective phenomena of taste, or those 

 dependant on excitation of the nervous apparatus of the sense by 

 internal causes. The various tastes which are experienced in disease 

 are probably occasioned by depraved secretions in the mouth acting 

 as foreign substances on the papillae. The epithelium of the tongue, 

 it is well known, is very prone to accumulate in the form of sordes, 

 loaded with unnatural materials ; on the removal of which, the natu- 

 ral taste is, in a great measure, restored. Majendie observed that 

 dogs, after the injection of milk into their veins, licked their lips, 

 and gave other signs of tasting. Such phenomena, if uniformly 

 present, might be occasioned by the transudation of the fluid from 

 the vessels to the nerves of the papillae. 



On the subject of taste we refer to the general treatises already cited ; to 

 Magendie's Physiology ; Rudolphi's Physiology ; Horn, liber den Geschmacks- 

 sinn des Menschen, Heidelberg, 1825 ; Panizza, Kicherche Sperimentali sopra 

 i Nervi, 1834, given by Dr. G. Burro wes in Med. Gaz. vol. xvi. ; Dr. Alcock, 

 Med. Gaz., Nov. 1836 ; Dr. Jno. Reid, Brit, and For. Med. Rev. vol. v. p. 309 ; 

 Valentin, de funct.nerv. p. 116. 



END OF THE FIRST VOLUME. 



