Part 7

51. _At eight years off, the gum of the lower corner tooth has become square, and the lower tush blunt._ The original drawing was made from the teeth of that noted horse, Oakley; and in order to render it as perfect as possible, the mouths of mares (Meal, Edgworth, Bess, &c.) have been compared. The departure from the circular form of the gum, as depicted in the coloured engraving, is even more marked than it was at the seventh year. Added to this change of figure, the gums appear more hard and less delicate; the mouth looks more firm, and seems to have attained the perfection of its strength. The margin of the lower jaw is now comparatively sharp, and the cheeks are flat. The crusta petrosa on the upper teeth is in a great degree removed; the enamel not yet, however, having a marked yellow tinge. On the lower corner incisors the crusta petrosa may still continue, but it no longer has a dull brown aspect: it is never prominent at this age, but rather speckled over the outer surface, than regularly enveloping any portion of it. It has a somewhat rough and worm-eaten aspect, and in colour is nearer to a dirty yellow than a dull brown. If the posterior angle of the upper corner incisor is pendant, or exhibits that species of notch, which was alluded to in the previous paragraph, it is at the eighth year well shown, and the table has undergone considerable alteration. There is now on the shell tooth, a full table, the infundibulum of which, if not obliterated, is always of lessened size, well marked out, and on all sides surrounded by a broad and a flattened surface. The other teeth have also changed their figures. The tables of the centre nippers have taken on a decided angular shape, and those of the lateral display no dubious tendency to assume that form. The infundibula may be obliterated, but more generally those in the lateral and corner teeth are retained, or if now absent, the circle of enamel will, on inspection, show that the cavity is only filled up by crusta petrosa, not absolutely worn out. The following wood-cuts exhibit the changes which the tables undergo; and as the eighth year is an important one, inasmuch as the horse which has attained it is called "aged," a double set is here introduced, to show the difference of figure which these parts may present. In those tables, it will be seen the infundibulum has gone from a central nipper only; but even in that instance, a white mark indicates that the cavity is merely filled up by crusta petrosa, the enamelled lining not being yet worn out. The alteration in the form and magnitude of the infundibula cannot, if the accompanying wood-cut be compared with those which have preceded it, fail to strike the reader; indeed these changes, aided by the worn appearance of tables of the shell teeth, are now the principal guides when judging of the age by the mouth.

52. _After the eighth year_, there is no certainty in any opinion drawn from the teeth. A guess may be hazarded, and very often that guess will prove correct, but at the same time it should be received only as a conjecture. The chance of naming the age decreases as the number of years increase. After the twelfth, the probability of hitting the exact year is very small. After the sixteenth year, all is confusion, and there remains no sign which could warrant any person in pretending he could pronounce the age by the teeth. It is true that certain tokens may induce a conviction that an animal is much older than sixteen, and this conviction may be so justified as to amount almost to a certainty; but no man, I imagine, could form any opinion with regard to the number of years by which a horse exceeded sixteen, or pronounce a decision that should have any appearance of exactitude. They who pretend to an ability of this kind, may, in a few solitary instances, strike the point; but repeated failures will show that there is no positive principle in operation to guide the judgment. Indeed the age is most correctly told during the periods of dentition, and up to the sixth year. After the sixth year, the certainty is not so great, but a very fair, if not a positive judgment can be pronounced until the eighth year is accomplished. After the eighth year, no man should give an unqualified opinion concerning the age of a horse. After the twelfth, whatever may be pronounced should be offered only as a conjecture; and, after the sixteenth, the practitioner had better be silent. When stating this the author must be understood as expressing the conviction at which almost exclusive attention to the subject, and much necessary consideration, has enabled him to arrive. It must not, however, be thought that he is arrogating a power of measuring the capabilities of genius; his wish is only to declare the truth as he perceives it. The intention to publish a work upon the teeth has not been concealed; opinions have been solicited and information sought; the author has many obligations to acknowledge; all to whom he has made application have been liberal in their communications; but from no one has he been able to obtain anything opposed to the conclusions he has here promulgated. It may be that hereafter the power of judging of the age shall be extended. Pessina and the Girards thought it could be done with exactitude up to an extreme point, and saw a principle in the latest changes which the teeth undergo. The general experience in this country, however, seems to have decided that, after the eighth year, there is no certainty. With that decision the author is reluctantly obliged to acquiesce, and even to add that certainty is not to be obtained after the sixth year. This limitation, coupled as it is with a confession of inability, may seem to be a backward movement; but truth cannot retrograde. By ascertaining how far our present knowledge leads us, a motive is given to genius by the opportunity created for its exercise. No pains have been spared to investigate the hypotheses which have been made known; they have been candidly put to the test, and on the proof of their inefficiency discarded. That the reader may judge for himself, the tables of teeth, and mouths of various ages are presented. The altered aspect of the tables at the ninth year is indicated in the following wood-cut, which exhibits these surfaces as gaining depth and narrowing from side to side. This appearance they generally assume, and at the same time the infundibula are either lost or much contracted.

The next wood-cut, which depicts the form of the tables at the tenth year, though true in its general character, will serve to show how far dependence may be placed in ordinary signs, since the infundibulum of the lateral nipper shows a well-marked cavity, while from the other teeth it seems to be upon the eve of disappearing. On inspection, however, it will be seen that in figures the tables approach more towards the square, which is the last form these surfaces assume.

53. _At twelve years old, there may be tartar on the lower tush. The teeth are longer, narrower, and the enamel darker._ The coloured engraving, which was, on the last occasion justified by a comparison with the mouth of that famous horse, Charles the Twelfth, will convey a general idea of the prevailing characteristics of this age. The teeth have lost the white and firm set aspect they bore at the eighth year. Often, at this period, they have, by wear, become irregular generally, as exhibited in the plate; the grooves, extending down the length of the upper incisors, contain the remnants of the crusta petrosa, which is almost black. The upper tush is usually much diminished, while the lower is long, especially in stallions kept for service. The teeth project more outward and begin to arrange themselves more in a line, no longer showing the crescentic order which they assumed at five years old. Also, by the twelfth year, the tongue, when the jaws are closed, protrudes from the open space between the incisors and molars. The degree in which these alterations have taken place, together with the protrusion of the incisors, is all that is present to guide the judgment; and practical experience is needed, to give him, who attempts to decide upon such weak evidence, any chance of success. As in cases of this description every thing that can help the judgment is eagerly seized upon, the general appearance of the animal is always to be considered; and that may warn the practitioner to modify his opinion. The lower jaw is sharp, the cheeks flat, and around the tushes there may be an accumulation of tartar. It is true the tables, consequent on the wear of the teeth, will have undergone some change, but that alteration is now so slightly marked as not to enforce itself upon the observation. It is easily overlooked, and by no means easily recognised. The annexed wood-cut will suggest the nature of the change. In it will be seen a further remove from the oval form of these parts in the young mouth. The surfaces have become square or angular, and the corners are only sufficiently rounded to indicate what once was the shape which they exhibited.

The following wood-cut depicts the tables at the completion of the fourteenth year, and only by careful comparison could the increase of age which they denote be detected. On inspection, however, it will be seen that the irregularities of outline are less prominent even than at the twelfth year.

54. _At sixteen years old, when the teeth are viewed from the side, only two incisors can be seen in the lower jaw_, as depicted in the coloured engraving, which was last authenticated by the mouth of Muley Moloch, which favourite stallion I was, by the kindness of Mr. Theobald, permitted to examine at his well-known establishment, where I also saw many other horses of the purest blood and highest promise. Of the excellence of the arrangements and the value of the animals, which give character to that gentleman's establishment, it would be presumption of me to speak. I have only to express my admiration of what I beheld, and tender my thanks for the attention I received. The engraving, however, was fortunately corroborated, and its general indications may therefore be accepted. The enamel has entirely lost its white and pearly tone. The tushes, perhaps, loaded with tartar in both jaws, are blunt, and generally either very short or long, inclining somewhat outward. The extension of the crescentic arrangement of the lower teeth enables only two to be seen when the parts are viewed from the side. The tongue protrudes to an obvious degree, and the saliva runs from the mouth when the jaws are separated. The edge of the lower jaw is very sharp and somewhat retracted, while the incisors have taken a horizontal direction. No sign, however, save the protrusion of the tongue, is positive. The general character is that of advanced age, and this general character, at once recognised by the eye of experience, is more to be depended upon than the teeth themselves. The teeth have now assumed the permanent character of old age; and in the figure of the tables will undergo no further alteration upon which any dependence can be placed. Up to the sixteenth year, however, the tables deserve to be consulted. Below is exhibited such evidence as they present, which the reader will perceive is so nice and delicately marked as to be easily misinterpreted. In the tables which belonged to the fourteenth year, it will be seen the infundibula are almost gone, a speck alone denotes their latest trace; nevertheless, the next wood-cut, which exhibits the tables at the sixteenth year, will show that the absence of the infundibula is not to be relied upon. Still the advance in age is, though feebly, indicated. The central incisor has assumed a form which is peculiarly characteristic of age in the horse. It is seldom that at sixteen years all the tables take so marked a shape, but some of them, and generally those in the centre, will, at this period, be symbolical of the truth.

Had it not been for the very conspicuous indication of the central tables, the others in the former wood-cut might have been reasonably decided to be more juvenile in their aspect.

55. _At twenty years old, the form of the mouth has changed, and the lower teeth are imperfectly seen from the front._ This circumstance springs from the more horizontal direction which the teeth have now assumed, and the acuteness of the angle which they consequently form when closed. The engraving also depicts that alteration in position which disables a person, standing in front, from well seeing both rows of incisors when the lips are separated. When the upper incisors are fairly presented to the sight, a partial view only of the lower teeth is obtained, and as the age advances even that is lost. Further inspection also shows additional changes in position, shape, and tint. The grooves are broad, deep, and well marked by their dark colour. Between the upper incisors there are interspaces in which the food has accumulated and become black, giving to the mouth the appearance represented in the coloured plate. The upper tush, which is now of a brownish hue, may be worn to the gum, and the lower continue long and surrounded by tartar, or both may be reduced to mere stumps. The tongue protrudes greatly; the membrane of the mouth seems hard; and no longer vascular, it is thrown into wrinkles. The edge of the lower jaw is sensibly retracted, and its sides are flattened or narrowed. The general appearance indicates the decay of nature. Here again, however, nothing is positive, save the yellowness of the teeth and the protrusion of the tongue. The general character of the animal is of more value than the indications of the mouth; and, persons familiar with horses can, sometimes by this, guess the age of an animal with the same approach to accuracy, which most people exhibit, when pronouncing the extent of an individual's life, by simply looking at a man's face. In neither instance, perhaps, could the basis of the opinion, which possibly shall approach very close to correctness, be accurately stated. Proof, as to the evidence upon which a conclusion is in such cases based, cannot be anticipated, and to the inquiry how they were able to tell the age, each would probably answer, by the "looks," but neither would be capable of precisely defining in what these "looks" consisted.

56. _At thirty years old, the jaws are contracted; the lower are not seen when the upper teeth are in view._ The coloured engraving, which at first sight seems to suggest that the animal possessed only a single jaw, exhibits the mouth as it appears at the thirtieth year. The animal, the mouth of which is here depicted, had a lower jaw with excellent teeth considering its age, but without elevating its head these could not, while the mouth was closed, be seen, or when seen, the view of those in the upper jaw was lost. This peculiarity arises from the teeth having taken a still more horizontal inclination; they are now crowded together; and, from the irregularity of their wear, may assume the pointed figure indicated in the plate. The change of colour also has become more decided, and the general indications, which have been before alluded to, are more marked. After what has been so frequently repeated concerning the deceptive character of the tables in extreme age, little, perhaps, need be added to that subject. Nevertheless, to convey an idea of the appearances which these surfaces may assume, subjoined are wood-cuts taken from authenticated mouths, for the inspection of which I am indebted to the liberality of Mr. Ernes, of Dockhead, who has paid great attention to the changes of the teeth. To the honour of that gentleman, I may, while confessing the heavy obligations under which his generosity has placed me, here mention, that no member of the veterinary profession had, to my knowledge, under his care so great a number of animals working at a period of life when the horse is usually supposed to be worthless. The majority of these were in good condition, active, and capable of doing every kind of ordinary service. They presented a pleasing spectacle, more than creditable to the talent of him under whose charge they had retained health and vigour. The aspects which the tables of the teeth exhibited, however, were such as set judgment at defiance, and for the purpose of enabling the reader to form his own opinion on the matter, engravings of a few of them are here introduced.

The above wood-cut exhibits the tables and arrangement of the incisors as they were seen in the mouth of an animal which was proved to be no less than twenty-eight years old. Any one, who should base his opinion solely on the marks, must have pronounced the creature to have been no more than five, since none of the infundibula are lost. The semi-circular arrangement also had suffered no very material change, and altogether the contrast with the next representation of the same parts, as they appeared in the mouth of a horse which was but one year older, is very striking.

In the above engraving the teeth are seen to be ranged almost in a line, which is the form they have a disposition to take at this great age. The appearance, here delineated, is more true than the foregoing in its general character, the infundibula being entirely worn out; for the specks in the centre of the tables show, not the remains of the last portion of the marks, but the exposure of the upper extremity of what once was the cavity of the pulp. In the next wood-cut, however, which depicts the tables of the teeth which were in the jaw of a horse, that had reached its thirtieth year, and from which the drawing for the coloured engraving was made, displays a portion of the infundibulum still retained in the corner incisor. The true character of age nevertheless is conspicuous in the form of the tables.

Such contradictory indications admit of being to a certain degree reconciled. The representations of the tables are correctly given, but, in the living mouths, these were corrected by the appearances of the teeth themselves. The incisors of the horse which was twenty-eight years old had suffered but little wear. An unusual degree of hardness, or an extraordinary power of self-preservation, contributed to keep them, so far as the tables were concerned, in appearance, young, long after the season of youth had passed. Almost from the fifth year the tables would seem to have suffered but a very gradual change; for even when twenty-eight, these parts do not indicate the horse to be more than "aged." The absence of wear may, in some measure, be attributed to the kind of food which the animal had consumed, it having been chiefly fed from the manger; and also to its being of a quiet disposition, or not inclined to bite and snap when the groom was dressing it. The want of wear, however, did not necessitate the cessation of growth, which went on at the natural rate; therefore, though the tables had a very youthful look, the teeth were, nevertheless, unusually long, and gave to the mouth a decided appearance of age. Their colour, and the removal of almost every vestige of the crusta petrosa, together with the general appearance of the horse, was sufficient to awaken those suspicions which would warn the practitioner. The eccentricities, however, which particular parts can exhibit, will teach the student, that a conclusion should only be drawn from observation and comparison of all the various signs which the teeth present. No sign can be singly relied on; but, by weighing the evidence, and placing the contradictory indications in opposition, something approaching to truth may, even in extreme age, be deduced; though such deductions, for obvious reasons, ought to be expressed with caution, and never, under any circumstances, positively advanced. Mr. Henderson, the respected veterinary surgeon to Her Majesty the Queen Dowager, possesses in his museum many interesting specimens of the teeth. Among the rest, he has the jaw of an animal which was ascertained to have reached the thirty-eighth year. This preparation, however, exhibits no sign that could characterize the extreme age which the horse had attained, and I allude to it, only as a confirmation of the opinion I have expressed, that, as the period of life advances, the mouth of the horse becomes more and more difficult of interpretation.