Important Research Work On Nerves In Dentin

In the British Dental Journal of June 15th, 1936, Stewart gave an excellent summary of the work done to date in connection with the innervation of dentin. He pointed out that the ultimate destination of the nerve fibrils of the pulp had never been satisfactorily determined, and that theories concerning the matter were the product of two distinct schools of thought. One theory is, substantially, that although the dentinal fibres are not nerves, they are probably responsible for conducting nervous impulses from the dentin to the pulp, the dentinal fibres ending in the outer layers of the dentin. It was first formulated by John Tomes. Stewart makes the interesting statement. “The odontoblast cells are mesodermic in origin, and it is generally accepted that mesodermal tissues do not conduct nerve impulses.” An altogether different theory is that neurofibrils from the pulp enter the dentin, but the depth to which they penetrate the dentin has not yet been determined. This has the support of many eminent investigators, and would appear to be more acceptable on clinical grounds. The difficulty hitherto confronting workers on this subject has been that of positively identifying neurofibrils. Dr. Charles E. Allen, Lecturer in Dental Materia Medica, University of Melbourne, has published a paper in The Australian Journal of Dentistry on The Innervation of Human Dentin, together with photomicrographs which he claims offer convincing evidence as to the presence of nervous tissue within the dentin, and indicate the depth of its penetration. Dr. Allen’s method has been to present the development of the dentin from the time when it is represented by nothing more than a mass of homogenenous cells (the dental papilla), tracing all the evolutionary changes which take place in the production of the finished tissue. This permits a demonstration of how a so-called “mesoblastic” tissue becomes converted into nerve tissue.
It is contended that Maximow’s dictum that “nervous tissue arises from the external layer of the body, the ectoderm,” is incorrect. Dr. Allen traverses the constitution, fertilization and segmentation of the ovum, and submits that there is no differentiation in to “primitive” layers, i.e., ectoderm, mesoderm and endoderm. All these cells are mesodermal, or connective tissue cells, and it can be proved that epithelium is formed form them. Neither the ectoderm nor the endoderm are primitive layers. They are secondary, not primary structures. They are fundamentally “mesoderma” in character.
A supposedly ectodermal structure, therefore (that is, nerve) can evolve from mesodermal cells without necessarily passing through an ectodermal stage, and can be formed in situ. The formation of dentin and its nervous supply in considered with special reference to original photo-micrographs accompanying the article, and the writer’s conclusions are lucidly and cogently presented. These conclusions are summarized as follows: –
The dentin is innervated throughout its extent, primarily by medullated neurofibrils traversing the dentinal canals, and partly by fine non-medullated fibres which are found in the ground substance or matrix.
The neurofibrils found in the dentinal canals are identical with Tome’s fibrils, and give off the fine non-medullated branches mentioned in the paper.
Definite and organs and nodes of Ranvier have been demonstrated in the dentin.
The Magazine and Oral Topics

The Cop
There have been advanced a number of stories as to the origin of the word “cop” as applied to policemen. The word cop is supposed to be derived from the Old English verb to cop, meaning to catch, to get hold of, to nab. This meaning to grab; to make away with something sought by others. In England, a policeman is often called a copper, that is, one who cops or catches offenders.
As applied to a policeman, the word cop dates back to 1859. The verb cop, as used in dialect English, has been traced back to the Seventeenth century. There is no evidence that cop was originally the abbreviation of constabulary of police.
Another story of the origin of the word is connected with the following: In 1829 Sir Robert Peel organized the firm modern police force in London. Members of the police force wore blue uniforms with very large copper buttons. These buttons gave the police the name copper, shortened to cop.
-Literary Digest.