[Ill.u.s.tration: FIG. 37.]

[Ill.u.s.tration: FIG. 38.]

As in other cases, it is necessary to fix an approximately normal standard for the ear from the standpoint of man's status in evolution. The ear grows more or less through life, but, like the skeleton, practically reaches its full development about the twenty-sixth year. That this is not always the case, however, is demonstrated by the results of the examination of 546 persons. In an examination of 63 children between 6 and 18 months old the ears measured from 160 to 212, the average being 190 inches; in width from 75 to 1, with an average of 96. In 127 children from 8 to 12 years old the ear measured from 195 to 232 inches, the average being 219; width 81 to 150, the average being 106. In 356 persons between 12 and 50 years old the shortest ear was 2, the longest 3, the average 250; width, smallest 1, largest 150, the average being 122 inches. The normal ear, or rather the ideal one (for few persons possess it in its entirety), should have a gracefully curved outline, be nowhere pointed or irregular, have a well-defined helix, separated from the anti-helix by a distinct scaphoid fossa extending down nearly to the level of the anti-tragus (Fig. 38). Its root should be lost in the concha before reaching the anti-helix. The anti-helix should not be unduly prominent, and should have a well-marked bifurcation at its superior extremity. The lobule should be shapely, not adherent, not too pendulous and free from grooves extending from the scaphoid fossa. The whole should be well shaped, and its proper proportion and size may be inferred from the table just given; in the adult it should not average over two and a half inches in length and one and a quarter in breadth.

The aural deformities that fall under the head of stigmata, or have been cla.s.sed as such, affect all portions of the external ear. The helix may be imperfect, it may be angular, from Darwin's tubercle it may lack its inward roll, it may be interrupted, the root of the helix may extend inward completely across the concha, and in very rare instances it may be bifurcated. The anti-helix may be unduly prominent or be insignificant; the scaphoid fossa may extend through the lobule or be triple.[213] The lobule may be adherent and sometimes almost absent, thus producing the jug-handle-shaped, or so-called Morel ear. It may be exaggerated in size; the whole ear may be misshapen, too large or too small. These deformities may exist in nearly every degree, only when p.r.o.nounced can they be considered as stigmata. Others have been noted, but their importance as signs of degeneracy is not very significant unless they co-exist with several of those above mentioned.

[Ill.u.s.tration: FIG. 39.]

The ears of degenerates frequently grow in later life to an enormous size.

On examination of 207 paupers over 50 years old the shortest ear was found to be 225 inches, the longest 336; the average on the right side was 273, on the left 276; the narrowest ear was 88, the widest 150, the average 126. These results, compared with the results of the measurements of normal persons from 12 to 50 years, plainly demonstrate that the ears of degenerates grow after the twenty-sixth year, when the skeleton has completed its development. With such large ears other stigmata are generally a.s.sociated. A few of the best types of stigmata of the ear ill.u.s.trate better than any description the general characteristics. Fig.

39 ill.u.s.trates the ear _par excellence_ of degeneracy, the typical jug-handled ear first described by Morel and called by his name. This consists of a long, narrow ear attached its entire length, and tapering upward and outward from the lobe to the point where the Darwinian tubercle is located, and there it may take any shape--round, straight, or pointed--as ill.u.s.trated in the drawing. The most singular deformity of the helix is the tubercle of Darwin, which is a little blunt point, projecting from the inwardly folded margin or helix. When present it is developed at birth and, according to Ludwig Meyer, more frequent in men than in women. Fig. 40 shows ear and tubercle taken from Darwin.[214]

These points not only project in toward the centre of the ear, but open a little outwards (Fig. 41) from its plane, so as to be visible when the head is viewed from directly in front and behind. They are variable in size, number and somewhat in position (Fig. 42), standing either a little higher or lower, and they sometimes occur on one ear and not on the other.

Another marked form of ear degeneracy is one in which the ear is developed backward at an angle of about 45 (Fig. 43). The general outline of the ear is fairly good. The anti-helix is much larger than it should be.

Degeneracy usually extends deeply into the organisation of those in whom this ear is present.

[Ill.u.s.tration: FIG. 40.]

[Ill.u.s.tration: FIG. 41.]

[Ill.u.s.tration: FIG. 42.]

[Ill.u.s.tration: FIG. 43. EAR ALMOST HORIZONTAL AND AT RIGHT ANGLES WITH THE HEAD.]

[Ill.u.s.tration: FIG. 44. EAR ALMOST ROUND WITH THREE DARWINIAN TUBERCLES AT INNER BORDER.]

[Ill.u.s.tration: FIG. 45.]

Fig. 44 ill.u.s.trates noticeable stigmata. The ear stands at right angles with the head. It is, however, almost as broad as it is long and differs in shape. The outer helix is excessively developed. The scaphoid fossa extends through the lobe, which is continuous with the body of the ear and is not distinct. The root of the helix is excessively developed. There are three Darwinian tubercles on its border. The anti-tragus is undeveloped.

The tragus is very small and divided into two parts. The auricle-temporal angle, for functional purposes, should not exceed, according to Buchanan, 30, or be less than 15. The difference in this respect is not clear, since free movement of head and body will readily adjust the auricle to receive sound. For functional purposes it would seem that the construction and shape of the ear, especially the anti-helix and concha, would be of greater importance than its position to the head, since it is necessary to collect the waves of sound for transmission. From a degeneracy standpoint, however, the position of the ear is important. Frigerio,[215]

from the examination of several hundred subjects, concludes that the auricle-temporal angle undergoes a gradual progress from below 90 in criminals and the insane to above 90 in apes. He found the large angle very marked in homicides, less so in thieves. There is no question but that Frigerio is correct in regard to this point. In an examination of the ears of 465 boy criminals at Pontiac, it was found that 198 were close to the head, or from 10 to 15; 152 at an angle of 45, and 115 at right angles or 90. Of 1,041 criminals at Elmira 285 were close, 567 at an angle of 45, and 187 at right angles.

[Ill.u.s.tration: FIG. 46.]

[Ill.u.s.tration: FIG. 47.]

[Ill.u.s.tration: FIG. 48.]

[Ill.u.s.tration: FIG. 49.]

Fig. 45 shows the ear which Hawthorne gives Donatello in the _Marble Faun_; it has been called the "Satanic" ear, because of the pointed extremities and its narrowness. The helix is rolled upon itself its entire length, giving the impression of great thickness. The anti-helix is excessively developed. Figs. 46, 47, 48 (ears of three illegitimate children at birth) show different stages of development as well as marked stigmata. Arrest of development occurs between the fourth and fifth month, owing to the trophic nerve centres being affected by the malnutrition of the mother. Fig. 49 exhibits the development of a congenital, elephantine ear in monstrosities. The resemblance to the large ear of the orang and chimpanzee is very marked.

CHAPTER XIII

THE DEGENERATE TEETH AND JAWS

Next to the ears, the jaws and teeth (as was to be expected from the variability of these organs in allied animals) are most affected by degeneracy. This is particularly true of the vertebrates, especially mammals, as might have been antic.i.p.ated from their phylogeny. At the head of the vertebrates is man; at the foot is the lancelet (amphioxus), which is perhaps most akin to those semi-vertebrates the ascidians, who, in their larval phase, are higher than when adult, and whose life-history excellently ill.u.s.trates that potent phase of evolution, degeneracy.

The lancelet has a spinal cord enclosed in a half-gristly ca.n.a.l (the notochord). It is practically dest.i.tute of a brain. The cerebral vesicle which represents this is a plain cavity without true subdivision into ventricles. There is no cranium. The eye (central in position) is a mere pigment spot with which it is able to distinguish light from darkness. The nose (behind this) is a small pit, lined with cilia, for purposes of smell. Into this the cerebral vesicle of the larval lancelet opens. The mouth is well guarded against the intrusion of noxious substances which have to pa.s.s through a vestibule richly provided with sensitive cells, resembling the taste buds of the human mouth. There is no heart. In this, as in the case of the eye, the lancelet is lower than the ascidians, the insects, crustaceans, and many molluscs. It approximates those worms which, despite a very elaborate vascular system, are dest.i.tute of a heart, the function of which is performed by contractile blood-vessels. From an embryologic and morphologic standpoint the proximate ancestor of the vertebrates may have been a free swimming animal, intermediate between an ascidian tadpole and the lancelet, and the primordial ancestor, a worm-like animal organised on a level with the star-fish. The vertebrates embryologically develop from this stage to the lampreys; thence to the cartilaginous fish (shark); to the amphibia (frog, toad, axolotl); to the reptiles; and thence to the oviparous mammals (duck-bill and echidna or spiny ant-eater); to the lemurs, and through forms like the _Pithecanthropus erectus_ to man. Mammal teeth pa.s.s, in evolution, from the simple types found in that oviparous edentate, the spiny ant-eater of Australia, to those of the indeciduous ancestors of the sloths and armadilloes, and their descendants, inclusive of the dolphins and whales, whose teeth, both in the fetal Greenland and adult sperm whale, preserve this old type. (The whales have degenerated from the hoofed mammals to suit their environment.) While, as in the edentates, these teeth may be few, they may also, as in the insectivorous marsupials, approximate those of the reptilia in number (sixty or seventy on a side) and characteristic location.

The evolution of this primitive tooth to the bicuspid and molar type has been explained by two theories: that of concrescence and that of differentiation.[216]

A number of conical teeth, in line as they lie in the jaws of the sperm whale, represent the primitive dent.i.tion.[217] In time a number of these teeth, according to the concresent theory, cl.u.s.ter together so as to form the four cusps of a human molar, each one of the whale tooth points forming one of the cusps of the mammalian tooth. Vertically succeeding teeth might also be grouped. What evidence is there in favour of this theory? and what is there against it? All primitive reptiles from which the mammals have descended, and many of the existing mammals, have a large number of isolated teeth of a conical form. Further, by shortening of the jaws, the embryonic germ from which each of the numerous tooth-caps is budded off in course of development could have been brought together in such a manner that any cusps originally stretched out in a line would form groups of a variable number of cusps, according to the more or less complex pattern of the crown. Against the acceptance of this theory stands the fact that cusps quite similar in all respects to each of the cusps which form the angles of the human molar are even now being added to the teeth in certain animals, such as the elephant, whose molar teeth cusps are being thus complicated. In the mesozoic period certain animals with tricuspid teeth occur. According to the theory of concrescence these teeth ought not to show any increase of cusps in later geologic periods, but down through the ages to the present time successors of those animals continue to present a very much larger number of cusps. How is this increase of cusps to be accounted for? Has there been a reserve store of conical teeth to increase the number? Most obviously to every student of the fossil history of cusps there is no reserve store, but new cusps are constantly rising upon the original crown itself by cusp addition.

In the Tria.s.sic occur the first mammalia with conical, round, reptilian teeth. There are also some aberrant types which possess complex or mult.i.tubercular teeth.

These teeth begin to show the first trace of cusp addition.

In Fig. 1, Plate A, the teeth of the dromatherium of the coal beds of North Carolina occur on the sides of the main cone, cusps or rudimentary cuspules. On either side of the main cone are two cuspules. In the same deposit occurred another animal represented by a single tooth (Fig. 3), in which these cusps are slightly larger. These cusps have obviously been added to the side of the teeth and are now growing. In teeth of the Jura.s.sic period, found in large numbers both in America and in England, but still of very minute size, are observed the same three cusps. These cusps have now taken two different positions; in one case they have the arrangement presented in Plate B. The middle cusp is relatively lower, and the lateral cusps are relatively higher; in fact these cones are almost equal in size. These teeth are termed triconodont, as having three nearly equal cones. But a.s.sociated with this is the spalacotherium, the teeth of which are represented in Plate A, Fig. 4. This tooth ill.u.s.trates the transformation of a tooth (triconodont) with three cusps in line into a tooth with three cusps forming a triangle. Here the primitive cusp is the apex of a triangle of which the two lateral cusps are the base. This tooth, in this single genus, is the key of comparison of the teeth of all mammalia. By this can be determined that part of a human molar which corresponds with a conical reptilian tooth. This stage is the triangle stage; the next stage is the development of a heel or spur upon this triangle (see in the amphitherium, Fig. 5). The opossum still distinctly preserves the ancient triangle. Look at it in profile, inside or in top view, and see that the anterior part of the tooth is unmodified. This triangle is traceable through a number of intermediate types. In Miacia (Fig. 6), a primitive carnivore, is a high triangle and a heel; looked at from above (Fig. 6a), the heel is seen to have spread out broader so that it is as broad as the triangle. The three molars of this animal ill.u.s.trate a most important principle, namely, that the anterior, triangular portion of the crown has been simply levelled down to the posterior portion.

[Ill.u.s.tration: PLATE A.]

[Ill.u.s.tration: PLATE B.]

These three teeth form a series of intermediate steps between a most ancient molar and the modern molar of the human type. The second tooth is halfway between the first and third. The second molar, seen from above, has exactly the same cusps as the first, so it is not difficult to recognise that each cusp has been directly derived from its fellow. The third tooth of the series (Fig. 7) has lost one of its cusps; it has lost a cusp of the triangle. It is now a tooth where only half the triangle is left on the anterior side and with a very long heel. That tooth has exactly the same pattern as the lower human molar tooth (Fig. 8), the only difference is that the heel is somewhat more prolonged. These teeth belong to one of the oldest fossil monkeys, anaptomorphus. Human lower molars, not very exceptionally, instead of four cusps, have five. The fifth cusp always appears in the middle of the heel, or between the posterior lingual and the posterior buccal. This occurs in monkeys and other animals, but no record exists of the ancient anterior lingual reappearing. The human lower molar, with its low, quadritubercular crown, has hence evolved by addition of cusps and by gradual modelling from a high-crowned, simple, pointed tooth.

Human teeth are of excellent service in the initial determination of degeneracy in the child. For this purpose the teeth should be studied from the first evidence of their development until they are all in place, which occurs normally, in most cases, by the twenty-second year.

Teeth-enamel is formed from the epiblast, and dentine, cementum, pulp (except as to nerve tissue) from the mesoblast. The enamel organs of the first set appear during the seventh week of foetal life; the dentine bulb during the ninth week. At this period the tooth obtains its periphery.

This models the enamel cap which fits over the dentine like a glove. When imperfections in hand or fingers exist these deformities are distinctly observed upon the glove, and in precisely the same manner are observed the different shapes and sizes of the incisors, cuspids, and molars.

Calcification of the teeth begins at the seventeenth week of foetal life.

The ill.u.s.tration (Fig. 50) shows the progress of calcification and development of the temporary set of teeth. Examination will show that any defect in nutrition, from conception to birth (due to inherited states or maternal impressions), has been registered upon the teeth. The state of the const.i.tution and the locality register the date of such defects. Thus if the tooth, as a whole, be larger or smaller than normal, or abnormally irregular, taint is undoubtedly inherited from one or both parents. If, on the other hand, there be defect at any part on the crowns of the teeth, and the contour be perfect, the date of malnutrition can be easily determined from this chart. More or less than the normal number of teeth, abnormally placed, demonstrates the existence of inherited defect, since the germs must have been deposited at the period mentioned. No absolute rule can be laid down as to date of the eruption of the teeth. The teeth of the temporary set erupt nearly as follows:

_After Birth._ _Time of Eruption._ Lower Central Incisors 7 months 1 to 10 weeks.

Upper " " 9 months 4 to 6 weeks.

Upper and Lower Lateral 12 months 4 to 6 weeks.

First Molars 14 months 1 to 2 months.

Cuspids 18 months 2 to 3 months.

Second Molars 26 months 3 to 5 months.

[Ill.u.s.tration: FIG. 50.]

[Ill.u.s.tration: FIG. 51. SHOWS LINES OF DEVELOPMENT OF THE PERMANENT TEETH.]