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THE POPULAR EDUCATOR. 



stomach and alimentary canal. The seat of the sense of taste 

 is the tongue ; but here again it is necessary to remind the 

 reader that the uses of this organ are not confined, as those of 

 the eye and ear are, to the reception of the impressions which 

 excite the sense. The tongue is, in its substance, a sheaf of 

 muscles, and it is largely employed in keeping the food between 

 the teeth, that it may be ground down, in crushing the softer 

 mass and mixing- it with the saliva, and in propelling it into the 

 throat. It is further employed as an instrument of speech ; so 

 much so, indeed, that in poetry, and even in common speech, it 

 is more prominently associated with this office than with any 

 other, and in this capacity has been the object of that powerful 

 and poetic description contained in the Epistle of James. 

 Nevertheless, since the organs of taste are distributed over the 

 surface of the tongue, it seems necessary to describe it as a 

 whole. If the reader will refer to the engraving, he will find 

 the surface of the tongue drawn as it would be seen if the whole 

 of the roof of the mouth and skull was removed, so that he 

 could look down upon it from above. The tongue covers the 

 floor of the mouth ; its border lies against the teeth. From the 

 tip it rises to its central part, then slopes away backward to the 

 throat, so that it nearly fills the closed mouth, and its upper 

 convex surface lies along under the concave palate. It has 

 great freedom, of movement, so far as its tip and edges are 

 concerned, but cannot be curled completely over and thrust 

 down the throat, because it is confined by a membrane, which 

 attaches the middle line of its under surface to the bottom of 

 the mouth. At one time it used to be the barbarous custom of 

 nurses to cut this membrane in new-born infants, a custom 

 which not unfrequcntly resulted in the child being choked by its 

 own tongue. It is with the upper surface of the tongue we 

 have to do, as there the organs of taste are found, and thereby 

 the food passes, seldom getting below the edges of the tongue. 

 The tongue is covered with a mucous, or slime-secreting, mem- 

 brane, and this membrane, on its upper surface, has a number 

 of little projections. Th.esc projections, or papillae as they are 

 called, are of three kinds,' named respectively circumvallate, 

 fungiform, and filiform papillae. The circumvallate papillae are 

 situated at the back of the tongue, and are from eight to 

 fifteen in number, ranged in the form of a V, with its point 

 backwards, towards the throat. They are of singular shape, 

 best explained by the small figure which gives both a section of 

 9ne of them, and half its surface. They each consist of a button- 

 like projection of the mucous membrane, surrounded by a 

 depression, and then an elevated ring which has another depres- 

 sion around it. They are called circumvallate, or walled round, 

 papillae, because they may be compared to a central tower 

 surrounded by a wall ; but the wall is a sunken wall, only made 

 by sinking two ditches, one outside and the other inside it. 

 The outside ditches of these miniature imaginary fortresses 

 touch one another, and that which lies behind the hindermost 

 ono is so deep as to be called the foramen caecum, or blind hole. 

 These papillae are the largest of all ; they are more powerfully 

 affected by flavours than any others, and it is thought that the 

 sapid juices run into the depressions around them, and thus the 

 sense of taste is agreeably prolonged. It will be seen from the 

 engraving that all the papillae have secondary ones ; biit while 

 the main papillae thrust up the outer bloodless coat' of the 

 mucous membrane before them, the secondary ones (i.e., the 

 papillae on the papillae) do not do this. 



The fungiform papillae are scattered irregularly over the front 

 two-thirds of the tongue, but are more plentifully distributed 

 towards the edges and tip than at the central part.' This 

 arrangement prevents the delicate papillae being crushed by the 

 tongue while it squeezes the food against the hard palate, while, 

 at the same time, they are so placed as that the juices of the 

 food so squeezed run off the summit of the tongue, and come into 

 contact with these little rounded eminences. Should the reader 

 examine his own tongue, he will perhaps not at once detect these 

 round "papillae, for they are obscured by the dense coating of 

 filiform papillae, which are, under ordinary circumstances, longer 

 than they. If, however, he press his finger on the middle of 

 his tongue, these round knobs will at once start out and become 

 visible, being distended with blood. If, further, a little 

 vinegar be placed on the tongue in a space between these 

 papillae, no taste is observed ; but if it run on to them, they 

 immediately erect themselves, and the sour taste is distinctly 

 conveyed. 



The filiform papillae cover the fore part of the tongue, running 

 in lines from the middle obliquely forward towards the edges, 

 and other lines of them run, outside those, round the extreme 

 point of the tongue. They are long and slender, and much 

 smaller than the others, and are surmounted by a tuft of threads, 

 consisting of thick epithelium (or outer bloodless layer); and 

 hence they look white or yellow, and impart to the whole top of 

 the tongue a light colour, which contrasts with the deep red of 

 its edges and under side. These papillae are probably rather 

 the iiltimate organs of touch than of taste. 



All these papillae are well supplied with blood-vessels, so that, 

 when the outer coat is taken off, they look, under the micro- 

 scope, to be little else than tufts of blood-vessels. Nerves 

 forming loops have been traced into them, and these are the 

 carriers of the sensuous impressions. These nerves proceed by 

 two different routes to the brain. Those which proceed from 

 the papillae (including the circumvallate) at the back of the 

 tongue, are gathered into a bundle which joins the eighth pair 

 of nerves; and those from the papillae at the front unite to 

 form a branch of the fifth pair. Each of these sets of nerves 

 conveys both common sensation and the special sense of taste ; 

 but the branch of the eighth is more concerned in carrying 

 gustatory impressions, for the sense of taste is keenest in the 

 large walled-round papillae, and the pleasures of taste become 

 gradually more intense in proceeding from the front backwards. 



Considering, then, the sense of taste in relation to its uses, 

 we find that not only does it stand at the entrance of the pas- 

 sage for food, to guard the gate, in order to admit good citizens 

 and exclude conspirators against the constitution, as the sense 

 of smell does, but it has other important functions. 



First, it stimulates to the act of grinding the food and reduc- 

 ing it to a pulp, giving, by the pleasure it occasions during the 

 process, an inducement which the bare knowledge of the fact 

 that this comminution is necessary for the after digestive opera- 

 tions of the stomach, could hardly supply. Secondly, from the 

 sensibility of the tongue becoming greater as the food proceeds 

 backwards, it causes it to be carried in that direction while 

 being masticated ; and finally, in order to enjoy the most exquisite 

 sensation of taste, the feeder finds it necessary to fling the bolus 

 backward on to the root of the tongue, and there it becomes 

 the subject of a curious mechanical process. Until the food has 

 reached this point, it is perfectly under the control of the will of 

 the feeder, and it can be moved in any direction, and entirely 

 ejected from the mouth, if he find it hard or nauseous , but 

 directly it has reached this point it passes at once out of his 

 control. The presence of food at this point excites what is 

 called the reflex, or involuntary, action of the muscles of the 

 throat, so that the soft palate above the throat behind seizes it 

 and thrusts it at once rapidly down into the stomach. This 

 involuntary action is curious, rot only because the presence of 

 food invariably excites it, but it cannot be excited unless by the 

 presence of some substance at that part. The act of swallow- 

 ing cannot be effected unless there be something to swallow. 

 Further, if a foreign body touch this sensitive part, and it can- 

 not be swallowed, the stimulus is so violent that, being denied 

 its legitimate result, it will excite the reversed action, and occa- 

 sion vomiting. Thus, while Nature ungrudgingly grants sensuous 

 gratification where bodily wants exist, she imperiously denies all 

 pleasure if no good end is connected with its gratification. 

 However sad the fact may be to him, the glutton knows that 

 there is a strict limit to his enjoyment. Alas for him ! he cannot 

 by any device revel in the pleasures of the table without filling 

 bis stomach, and this is of very limited capacity. 



In the case of taste, then, the mutual dependence of bodily 

 necessities and the gratification of the sense is very marked ; 

 and a consideration of the whole circumstances connected with 

 this sense will furnish a strong argument in favour of the unity 

 of the creation and the omniscience of the Creator; for we have, 

 as essential conditions of the pleasure of eating, four distinct 

 things, in no way necessarily connected with one another, except 

 as they are designed to relate to each other. They are these : 

 The body, requiring aliment ; the sense of taste, prompting to 

 feed ; wholesome food, fitted to maintain the body in well-being; 

 peculiar, and often superadded flavours, to tempt the sense. 

 Putting these in the order in which they are related to one 

 another, we have food, flavour, pleasure, health. The distinct 

 links in the chain are all wonderful, but the union proves a 

 unity of design and a benevolence of purpose. 



