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we have been describing are as follows, and we give them that the reader, when next traveling upon an English line of railroad and passing a signal-box, may give a passing thought of thanks to the inventor of the "block" system, and the gentleman who framed these rules, Mr. William Henry Preece, of the Institute of Civil Engineers, and to the individual, let us hope, who follows them closely-the signal-man:

INSTRUCTIONS.

1. No train or engine is to be allowed to pass your box unless the electric signal for the section into which it is about to proceed stands at ALL CLEAR.

2. When a train has entered the section of line which you have protected (under Rule 4), you will signal to the next station, two beats on the bell twice, to signify "Train coming; be ready."

3. On the approach or arrival of the train or engine at your box, you will, provided the electric signal stands at ALL CLEAR, at once signal it on the bell to the next station in advance, thus:

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4. This signal will be acknowledged by the corresponding station, by throwing his switch-handle over to "ON," thereby placing the electric signal at your station at DANGER, and protecting the line from any train following that already in the section.

5. You will acknowledge this signal by returning one beat of the bell. 6. On the arrival of the Down train at

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man at that station will pull his switch-handle over to OFF, thereby removing your danger-signal, intimating the arrival of the train and clearing the line.

7. This you will acknowledge by one beat on the bell.

8. In case any obstruction exists upon the line to necessitate its being blocked, give five sharp beats on the bell (which must be repeated), and raise the electric signal to Danger, which must be maintained as long as the obstruction lasts.

9. No signal is to be considered complete until it has been acknowledged.

I beg leave to state that this article is written without being at all acquainted with the system of signaling on American lines of railroad, so that I am unable to say how far our own bears comparison with the English system.

THE FACIAL ANGLE.

BY RANSOM DEXTER, A. M., M. D.,

PROFESSOR OF ZOOLOGY AND PHYSIOLOGY IN THE UNIVERSITY OF CHICAGO.

THE

HE methods of estimating the facial angle hitherto adopted by naturalists are all mere modifications of that proposed by Peter Camper, and consist in describing an angle with one line passing along the base of the skull, intersected by another which passes from the anterior portion of the upper jaw over the forehead.

Prof. Owen's definition is: "If a line be drawn from the occipital condyle along the floor of the nostrils, and be intersected by a second,

touching the most prominent parts of the forehead and upper jaw, the intersected angle is called the facial angle" (vol. ii., p. 572, "Anatomy of Vertebrates").

The relation of the face is not to the base of the skull, or the plane from the floor of the nostrils to its articulation to the backbone, but to the axis of the body; for the face, in the lowest class of animals that have a backbone, the fish, is in line with the base of the skull, the axis of the body, and the dorsal surface of the animal; and in man, the highest class, the face is in line with the abdominal surface, and axis of the body. But the base of the skull does not keep in harmony, but varies irregularly. Then, there are numerous other elements than the bones at the base of the skull, that are factors in the aspect of the face, as, the modified development of other bones of the skull, peculiar development of bones of the face, and relation of the bones of the face that are not attached to the skull, but to other facial bones.

To make the subject more clearly comprehensible, it will be necessary to trace more in detail the development of the division of animals to be considered.

The subject of the facial angle has occupied the attention of philosophers from the earliest antiquity. Their theories, though vague, unsatisfactory, and uninteresting in themselves, yet tend conclusively to show that some patent general principle underlies the whole domain of the subject. Confined, as they were, to the narrow limits of the varieties of the human race, they would get only a part of the evidence that is so beautifully illustrated, when we include the whole sub-kingdom of animals to which we belong.

At the beginning of the present century, Cuvier, Von Baer, and others, discovered and established the great laws of evolution. The laws thus elucidated were: 1. That the entire animal kingdom origi nates from an ancestral egg; eggs, too, though differing in physical appearance, that are quite similar in structure. 2. That every animal, in its evolution, had to pass through the several stages of ovulation, fertilization, germination, and development, before it could maintain an independent existence. 3. That in their development they assumed but few primary structural patterns or types.

After the promulgation of the above doctrines, a series of investigations ensued, which brought naturalists to approximate a general agreement that there are only five general morphological or formtypes of animals. Every animal, then, of the entire animal kingdom, must be classed in one or the other of these five sub-kingdoms, and each division thus classed has one fundamental plan of structure. The only way in which the animals of each sub-kingdom can differ is in the manner of executing their physiological functions.

In considering, then, any of the great physiological and philosophical questions that are based upon a uniformity of primitive type-development, we find that many useful lessons may be learned by including

in our considerations every class of animals in which the specialization to be considered appears. For example, every animal belonging to the vertebrate sub-kingdom of animals agrees with every other animal of the same sub-kingdom in the following distinctive characteristicscharacteristics, too, that we shall find involved in our considerations of the subject of the facial angle: In all, the head and vertebral column are composed of a number of definite segments, arranged along a longi

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tudinal axis; each segment of this framework is normally composed of a body and two diverging, ring-like formations; the dorsal containing the brain and spinal cord, the ventral, or abdominal, containing the organs of nutrition, as the alimentary canal, circulating and eliminating organs. Every vertebrate animal, then, is possessed of two tubes of framework: the one, to protect the brain and spinal cord; the other, the organs of nutrition. These tubes are subject to very great variation, and are modified, as by a master's hand, to meet the necessities that their various specializations of function may demand. The great modification in the calibre of the dorsal tube in different classes of the vertebrates, as well as the great variation in shape of the elements which compose that arch, is apparent to every one. In the region of the spine, the elements that compose the segments of the arch are rounded, and at some distance apart, while in the cranial (skull) region they are flattened, spread out, so as to unite and form sutures, thus making a solid brain-case, for the protection of the softer and more massive nerve-matter.

The elements composing the nutritive case are the jaws, ribs, and pelvic girdle. These, like the spinal elements, are subject to great modification, owing to the immense range of variation to which their specializations are subjected. The difference in the facial develop

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ments can well be imagined by calling to mind the various countenances of animals, from the fish to man. The angle of the face is simply and properly, I think, indicated by the relation expressed by two lines the first, or base line, corresponding to the axis of the body; the other, diverging, or face line, drawn from the anterior margin of the upper jaw, over the centre of the forehead. The relation and angles formed by these two lines, and their intersections thus indicated, express the relation and comparative development at the union of the two primitive tubes, the neural, or skull, and hemal (face), at the anterior extremity or head of a vertebrate animal.

As before stated, authors have hitherto established the base-line from the floor of the nostrils, to the articulation of the occipital bone to the vertebræ. This is a grave error, and one, no doubt, that has contributed its share to depreciate the subject as an index to the mental caste of a vertebrate animal. For, by adopting this method, we are subject to the enormous error of ninety degrees in passing through the sub-kingdom, all of which we lose, little by little, as we ascend the scale of animals of this type, or form of structure. And yet they make this application through the entire vertebrate series. Yet, by referring to the cut, we find the face of the lowest class of the type, the fish, to be in direct line with the dorsal surface of the animal, and hence the base and diverging lines are parallel; while, in the highest of the type, that of man, the face is in line with the ventral or abdominal surface. Again, after effecting a grand variation of one hundred and eighty degrees, or the half of a circle, the two lines are once more parallel.

What, then, are the factors in the phenomena of the great change of the aspect of the face, with such a modification of its constituents, from a line of the dorsal to that of the abdominal surface, all of which is effected by almost imperceptible gradations, as we ascend the series from the fish to man? It is by the modification of the anterior extremities of these cranio-vertebral canals in the development and increase of the cerebral hemispheres, which is that part of the brain that is recognized as the seat of thought, and their influence upon other

structures, that the whole change is wrought from a complete dominant power of the physical over the mental, to the reverse, viz., an entire dominant ascension, in some instances, of the moral and intellectual over the physical. In every vertebrate animal, then, there are two factors, the physical and mental; the facial angle is the typical expression or exponent of the relative strength or condition of each.

It may be observed that, with the ascension of these animals, the relative size of the brain-case, or skull, increases with a proportionate diminution of the bones of the face, and of the projection of the jaws in front of the orbits.

In the cold-blooded fish, the serpent, and the crocodile, the cavity for the brain is small, but little more than a prolongation of the canal for the spinal cord, with a disproportionate development of the organs of mastication, thus enabling them to execute the strongest instinct of the lower animals, namely, to slay and devour. In the bird class, the brain is somewhat larger, but is contained in the posterior part of the cranium, they manifesting but a slight mental superiority over the reptile. In the dog, over whom man is lord, and the noble horse, the brain is much larger; the facial line intersects at about a right angle with the base line, or vertebral axis. In these animals we begin to discover the rudiments of some of those more noble motives which are so abundantly lavished upon some of the higher animals.

The monkey and the anthropoid, or man-like apes, express in a very characteristic manner many of the mental attributes of the lower varieties of the human species. Nor is this to be wondered at, when we consider the close anatomical relation which subsists between the two, and the enormous development of the cerebral hemispheres as compared with the lower classes of the same type.

The profile of the idiot is the next introduced in the cut, to illustrate the influence upon the size and shape of the cranium, or skull, that an arrest of brain-development has wrought, and which corresponds to the mental manifestations of its subject.

The other three profile views represent the savage, the half-civilized, and the cultivated races of man. The first of the three, the one next to the view of the idiot, is a drawing from a correct engraving of the celebrated North American Indian chief Black Hawk, and corresponds in brain capacity, facial angle, and mental powers, very nearly to the other savage races, viz., the Malayan and Ethiopian. The next that is represented in the cut is the half-civilized Mongolian race, illustrating very nicely the ratio of the two factors, physical and mental. The last is a representation of the highly-cultivated Caucasian race, and is a correct profile view of one of the most illustrious statesmen that this or any other nation ever possessed-that of Daniel Webster.

In the lowest of the type, the fish, we find the brain least developed, and the cerebral hemispheres, or instrument of thought, bearing

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