# Transactions of the Provincial Medical and Surgical Association/Volume 1/Theory of the Frontal Sinus

THEORY
OF
THE FRONTAL SINUS.
BY E. MILLIGAN, M.D., F.S.A.
IT is not easy to say at what date or period of science, the eminences and various inequalities on the surface of the human skull first became particular objects of attention among medical men. They could not have escaped notice after the operation of trepan, or perforation of the cranium, when its fracture, or other diseases occasioning compression of the brain, had once been introduced; for, in that operation, such inequalities greatly increase its hazard, and call for the strictest attention from the most reckless practitioners. But the trepan, and these inequalities, were familiar to Hippocrates and to Aristotle, who wrote not very long after him, and beyond this period the history of medicine is obscured with fable. In the time of Celsus the attention to these inequalities of the cranial surface had not diminished. He warns us earnestly to attend to them, while delivering his minute precepts for the management of the trepan; he suggests that the prominence of the mastoid process is probably the reason why no hair grows on the scalp immediately behind the ears; and informs us expressly that the ​lower part of the skull is made rough with tubercles in order to assist in its nutation. This he may be fairly supposed to have explained, by imagining that they afforded longer handles or levers, into which the muscles performing these motions might be inserted: but, so much was the study of these protuberances neglected on the revival of letters, that there is no passage in all Celsus which has occasioned more dispute among his commentators; see Luchtman's Celsus, lib. vii. c. I. Indeed, there is not much to be learned by them at any time, and Vesalius observing the superstitions that began to be attached to them in his day, did much to lessen their importance. The first Monro, Haller, and Albinus, showed that it is the soft parts that give form to the hard parts in contact with them, and not the hard that give form to the soft; a proposition easily deduced from the absorption naturally effected by the impetus of circulation, and which, consequently, becomes greatest in those tissues which are made to suffer all the shock of a lively circulation, but possess not an equally active preparative force to make restitution for the waste it occasions. Hence those projections on the surfaces of bones being found greatest where the muscular action had been most vehement, were generally imputed to this action alone; till the elegant ideas of Blumenbach on the nisus formativus and of Hunter on the diffused matter of life, brought reasonable men to see that the formation of all such parts is comprehended in the original design of the Author of the animal microcosm, and for the evolution of which, certain springs or forces have been impressed from the beginning upon the embryotic ​mass, which act as truly in response to their time and object, as the compound forces which exhibit and preserve the harmonious movements of the heavenly bodies, and of the developments of which, in fine, the muscles are not the cause, but the humble though frequently the modifying instruments. For our present purpose, this relation of the two actions will appear at once, by comparing the origin of the small styloid muscles with that of the powerful temporal muscle; where it is seen at once that prominence of the origins is in more than an inverse proportion to the force of the respective muscles, and that both are large in comparison to the attachments of the great pectoral and latissimus dorsi. Still as all such processes are very small in infancy, and are found to bear a constant proportion to the vigour of action in their muscles, the modified effect of the latter becomes equally evident.
Such was the state of science with respect to this subject, when a new superstition made its appearance, not among the frivolous gay denizens of the south of Europe, but in the schools of the deep thinking philosophic Germans. It was essential to this new doctrine to suppose that every enlargement of the cranium from without, corresponds to, and is occasioned by, some equivalent augmentation of volume in the brain within, namely, in that point of it which corresponds to the region of the external augmentation. To establish this doctrine, this craniology or phrenology as it more lately has been called, one of two things is necessary. It was to be shewn, either that the surface of the brain corresponds entirely with the convex surface of the ​cranium, or that, after allowing for various modifications of the latter as arising from various causes, it still essentially agrees with the surface of the brain, projecting where the brain projects, and receding where the brain recedes; but neither proposition can be maintained for a moment. A single glance of the eye, or a touch of the linger, evinces that, in many places where the brain recedes, the outer table projects; in others, as in the orbit, behind the mastoid process, behind the condyloid process, and behind the foramen magnum, where the outer table recedes, the brain on the contrary projects. Finally, except the general disposition towards an oval figure, they have scarcely any thing in common.
Lastly:─As the inner table every where adheres closely to the brain, whilst at some points the outer table recedes two inches from it, and in others, approaches within a quarter of a line, it is evidently not modified by the only interjacent body, the internal table, so as to bear in its expanded parts any certain or fixed relation to the brain within. Taking these two facts together, they afford an unanswerable demonstration of the fallacy of the averment, that augmented developments of the external table, correspond to internal developments of the surface of the brain, or of the organs marked thereon, at their pleasure, by writers on phrenology.
But this is merely rebutting the point maintained by a sect with whom it is impossible to be serious, without becoming, at the same time, ridiculous. What follows, although naturally arising out of the foregoing considerations, claims a brighter scope, and illustrates some hitherto unexplained phenomena ​in the structure and gradual formation of the human body.
If we contemplate the interior of a skull, we shall at once perceive that the inner table has every where penetrated as far as it could into the recesses which open on the surface of the brain. Every convolution has hollowed out its corresponding mould in the vitreous table; every fissure between the convolutions has its corresponding ridge on the same table. The alæ minores, the angles of the petrous portions laterally, the crista galli and spinous process before, the vertical and transverse spines behind, all shew the tendency of this table to adapt itself to the fissures of the encephalon; nor does it ever neglect to do so, except where strong membranes projecting from it, nourished by its vessels, tense like bone, and sometimes becoming bone, supply its place; it is smooth and glassy, as all bones are which are subjected to a gentle but never-ceasing motion; and evinces, by this single property, its perpetual contact with the brain, and obedience to the impetus of its double pulsation. Lastly, the inner table has no relation, no attachment to any organ whatever, except the brain, its membranes, and vessels. To the protection of this viscus it is exclusively devoted, and a sagacious anatomist might infer as much from the ordinary course taken by the meningeal arteries.
The diploë may be considered merely as the cellular tissue connecting the tables of the cranium. It was in this state in the cartilage before it became bone, and preserves its connecting relations to each, unaltered, without performing any other immediate function. For the meditullium, which it secretes. ​seems merely destined to promote its elasticity; and its elasticity is of the greatest service in diffusing local percussion, and thereby lessening the effect from external injuries upon the inner table and brain. By transmitting small blood-vessels in both directions, it merely performs another part of its connecting function.
We come now to the outer table. It is every where separated from the inner table by the diploë, except at the frontal sinus, and in the ethmoid, sphenoid, and basilar portion of the occipital bones, where it is generally formed into sinuses lined with a mucous membrane. The diploë, it is well known, contains no such membrane.
Considered in relation to the brain, the membranes, the inner table, and the diploë itself, the outer table presents no other definite organization beyond that of an irregular envelope, which is in some places as thin as a wafer, in others thicker than all the rest of the cranium. But, if we view it from without, we find that every particle of its surface is adapted to some purpose which it has to answer in combination with the soft parts with which it is in contact. Many processes are levers for the muscles; others are merely scabrous surfaces for their insertion; others are condyles for joints; others, organs of hearing; others, organs of fixation; others, of protection; and all this in direct reference to the organs in contact, but without the least relation, that can be discovered, to the encephalon. Hence we are forced to conclude that its projections solely originate under the influence, and for the completion of, functions that are all external ​to the cranium; and the same thing must necessarily be inferred of the external table, which is merely their substratum. These facts being established from observation, it is very easy to see how the frontal sinus, and other contemporary phenomena, take place. The evolution of the frontal sinus does not commence till the seventh year. At this time the bones of the face are still small and childish, the jaws occupied by the first set of teeth, and no acervus cerebri has yet been formed in the pineal gland. But the Wenzels inform us, from many observations, that, at this age of seven years, the brain has arrived at its full magnitude; and by inspecting their tables, copied in Milligan's Majendie, and taking the cube roots of the respective weights at seven, and the age of majority, it will be found that this averment comes very near the truth, and has only been disputed by those who did not understand how to make use of these tables. Now it is a law in the development of the system, that when any part has arrived at its full magnitude, there occurs a sensible diminution in the circulation of that part, which I have elsewhere named stagnation, re-stagnation, and stasis, but for which it is not easy to find a proper term. When this state occurs, less blood will necessarily pass into the internal carotid, and so much more will consequently be sent to the face and outer parts of the head by the external carotid, the other branch of that trunk from which they arise at the same instant, namely, the common carotid artery. Hence the infantile and puerile brightness of eye now gradually diminishes in splendour, because it is henceforth supplied by the waning powers of the ​internal carotid, while the complexion of the cheek, the volume of the face, the evolution of the teeth, the eye-brows, and the still small processes of the outer table of the skull, all sufficiently evince that the energy of the circulation has now found a new direction in the branches of the external carotid. All the parts to which this vessel carries blood, are, from henceforth, developed with nearly as much rapidity as the brain had been in the first septennial period of life. But among the bones hereby so rapidly developed, the nasal bones, the spongy portion of the ethmoidal bone, the external table of the os frontis and the ossa malæ, have their full share. But as the growth of all these bones, except the os frontis, is forwards, and as this bone always maintains an exact harmonic continuity with the other bones of the transverse suture, it is necessarily brought forward along with these bones. It cannot carry the diploië along with it, which substance not being so well nourished, will tend to become absorbed. The same effect will be greatly promoted from another cause. The schneiderian membrane growing at the same time with great rapidity, advances through the infundibular passages of the ethmoid bone, is now in immediate contact with the decaying fibres of the diploië connecting the two tables of the frontal bone, which may not yet be absorbed, and passing through amongst these, whilst the pulsation of its vessels causes them to be removed, it gradually scoops out for itself a wedge-shaped cavity between the two tables, which we denominate the frontal sinus. This sinus is not completed till twenty-one, or about the time when the bones of ​the face are fully perfected; but that this is the mode in which it proceeds, may be determined by inspection of the sinus in skulls, at the different ages from its commencement in the seventh year, to the period of its final development. Having given many facts in confirmation of this theory of the origin of the frontal sinus, in my notes to Majendie's Physiology, editions third and fourth, I shall not enlarge more on the matter here, but conclude by observing that this view of the frontal sinuses does not seem liable to any serious objection. The eminences, therefore, and development of parts, situated over the frontal sinuses, can have no relation to, or congruence with, the parts of the brain within.