After studying specimens similar to those from which these specimens have been made, I have been much better able to construct obturators for defective palates.

Both the medical and dental professions usually speak of the high arch of the mouth, as though the median line had been forced upward. If the floor of the nose of such mouths be examined no ele

vation will be found, except perhaps under the cartilaginous portion of the septum. The floor of the nose posteriorly is held down by the vomer, which is seldom deflected. The principal reason for the high arch or dome lies in the length and position of the alveolar process. Instead of passing outward and downward in a curved manner, it passes more downward and is more or less elongated. Therefore it is the position of the alveolar process that gives the appearance of a high arch, rather than the elevation of the center of

the mouth. As has been already said, this is brought about by the lack of the precisive force of the lower teeth against the upper ones. There are several factors which have more or less influence in modifying the shape and size of the maxillary sinus, the roof of the

5.

of

32.

1. Frontal lobe. 2. Meninges. 3. Corpus callosum. 4. Septum lucidum. Skin. 6. Occipito-frontalis aponeurosis. 7. Parietal bone. 8. Parietal lobe. 9. Splenium of corpus callosum. 10. Occipital lobe. 11. Peduncle. 12. Pons varolii. 13. Torcular of Herophilus. 14. Fourth ventricle. 15. Cerebellum. 16. Medulla. 17. Uvula. 18. Recti muscles. 19. Genu of corpus callosum. 20. Foramen Monro. 21. Anterior commissure. 22. Frontal sinus. 23. Crista gaili. 24. Optic chiasma. 25. Sphenoidal sinus. 26. Superior meatus. 27. Superior turbinate. 28. Middle meatus. 29. Inferior turbinate. 30. Inferior meatus. 31. Hard palate. Soft palate. 33. Uvula. 34. Genio-glossus. 35. Genio-hyo-glossus. 36. Epiglottis. 37. Glottis. 38. Fourth cervical vertebræ. 39. Inter-vertebral substance. 40. Trachea. mouth, the nasal cavity and the positions of the teeth, and among the most important of these are adenoid enlargements and congenital and acquired cleft palate. The partial or complete closure of the respiratory tract is sometimes caused by bony deposit near the pos

terior nares, which may or may not be congenital, but the most common obstruction in this region is in the form of adenoid growths. Fig. 5 is a marked illustration, showing the growth of glandular tissue of this region. It will be noticed that the space is almost closed. The enlargement passes forward as well as backward, causing a deformity of the nasal chamber. This condition compels the person to breathe through the mouth, which distorts the normal action of the various muscles of the pharynx, the tongue, of mastication, and of the face, and influences in changing the character of the bony structures. The occlusion of the teeth is also interfered with. The occlusion or constant pressure of one jaw against the other is one of the greatest factors in properly placing the teeth and in modeling the jaws, and through shaping the jaws the nasal fossa with its pneumatic sinuses and cells is influenced, and even the orbit and vision may be influenced by the enlargement of the adenoid tissue of pharynx. With such closure of the posterior nares the treatment for irregularities of the teeth must begin with the removal of these adenoid growths. If this is not accomplished almost all the mechanical appliances or interference with the teeth will be useless.

These are only a few illustrations selected from over one hundred slides which I have made from new frozen sections during the past winter. The work has been intensely interesting and I think would repay anyone who is at all interested in regional anatomy of the head and face.

Dr. James Truman, Philadelphia: Dr. Peirce has spent three years in working up the matter for this paper, and he is to be congratulated upon the result. I know the third molar has been a troublesome tooth to every practitioner, but in the earlier races it was quite a different molar from that of civilization. As peoples develop the jaw begins to recede and contract. I cannot agree with Dr. Taft's statement that this contraction is due to variations of food. These teeth are all developed in what is known as the follicular stage, and it is then that the contraction probably takes place, and as the jaw recedes backward these teeth suffer more or less compression and gradually develop smaller bodies. The idea that this development can be produced after the enamel is formed is contrary to all recognized theories of comparative anatomy and general histology. As to the third molar being lost, it may be crowded out of its proper place, but I doubt very much if it will ever be absolutely lost. This same condition of small third molars is found in civilized races thousands of years before the Christian era, and I don't think there has been any practical change in these teeth within the development of the present civilization.

Dr. Peirce, closing discussion: I commenced this examination of third molars with the belief that use and disuse modified structures, but I found it probable that other factors were at work. The fact that the third molar is better developed and more efficient in uncivilized than in civilized life is certainly strong evidence that a modification of diet has had its influence in the development of the tooth. When we find that savage people, who live largely by the chase and on raw and coarse food, have a better third molar than others higher in the scale of civilization, we cannot but infer that diet has influenced the tooth. In talking recently with a prominent scientist I asked his opinion regarding the influence of use and disuse. He replied, “I am entirely ignorant. For many years I believed that these were factors, but to-day I do not know." I must take the same stand. Statistics show that at least seventy-five per cent of the third molars of civilized people of to-day are reduced in size, and we must look for some reason. While I may still adhere to the view that use and disuse do modify structures, I am quite convinced that other factors with which we are not familiar also play an important part in the reduction of this tooth as well as of other tissues.

SECTION V. Continued.

Regional Anatomy.

PAPER BY M. H. CRYER, OF THE SECTION.

In 1885, when the "American System of Dentistry” was written, I had the honor of contributing the first two hundred and eighty-nine pages, the subject being "Regional Anatomy." At that time I thought the subject had been exhausted, but future surgical operations and dissections, carried on by other methods than those usually adopted in our dissecting rooms, proved that many statements of the general anatomists were erroneous, and that many important facts had not been brought to notice.

In 1895, at the meeting of the American Dental Association, the forerunner of this organization, I read a paper on the study of the maxillary bones, showing many new features of anatomy. At the meeting of this body in 1899 I read another paper on the same subject, still giving new ideas and facts upon the anatomy of the face. At this time it seemed that the subject had been nearly exhausted, and I began to compile the matter of various papers read before this and other societies into a book which has since been published, but even before this was completed I recognized that there was still much to learn from the surgical standpoint. It therefore gives me much pleasure to have this opportunity of presenting before the gentlemen of this Association some of my work of the past year.

The best teachers recognize that in order to guide the surgeon in his operations the study of anatomy for practical work should be done under such conditions as nearest approach life, and accepting this as a basis, many of our modern anatomists are following the plan of first injecting the body as soon as possible after death with a solution of formalin for hardening the soft tissues. The body is then covered with a coat of vaselin and wrapped in cloth or bandages to