ANATOMY. 



215 



c-f its colour, facts which should ever be remem- 

 bered by the practical surgeon in his treatment of 

 fractures. As our general anatomy of the bony 

 system would appear imperfect without noticing 

 those useful, but often ill-treated servants, the 

 teeth, we refer to the article Teeth, in the Encyclo- 

 pedia, for a description of the most prominent and 

 peculiar characteristics of their organization, ar- 

 rangement, and forms. 



Having now completed our short, but we flatter 

 ourselves comprehensive, sketch of the general 

 anatomy of the bony or osseous system, we shall 

 next attempt a brief topographical description of 

 the human skeleton, referring to Anatomy, Plate 

 III. in the first volume of the Encyclopedia, for a 

 more correct representation of the relative con- 

 nections, shape, and size, of such bones as are 

 brought fully into view in the anterior and poste- 

 rior aspects in which the skeleton is figured in the 

 plate. 



Anatomists have been accustomed to divide the 

 skeleton into the head, trunk, and extremities, and 

 the extremities have been again subdivided into 

 the upper and lower. Before, however, entering 

 into particular details, it is necessary to observe, 

 that all the descriptions in this article are to be 

 considered as applicable to the adult male, unless 

 when the contrary is expressly specified. 



To regulate the interpretation of the terms 

 anterior, posterior, lateral, above, below, before, 

 behind, &c. we shall uniformly suppose the 

 body to be in the erect posture, with the arms 

 hanging parallel to the trunk, and the palms of 

 the hands and toes turned directly forwards. 

 This is the simple remedy, and the only effectual 

 one, for the trifling ambiguity which might other- 

 wise attend the use of these terms. For example : 

 by superior and inferior is signified higher and 

 lower, with respect to the erect position. By an- 

 terior and posterior is denoted the situation of 

 the parts, as nearer to the surface or hinder sur- 

 face of the body, and by laterally is to be under- 

 stood that the parts so described approach the one 

 side or the other. Inner, and outer, and external, 

 and internal, express the situation of any given 

 part or portion of the body, or of an imaginary 

 plane bisecting the body into lateral halves, pass- 

 ing through the head and trunk, and continued 

 between the lower extremities. 



The Head. The united assemblage of bones 

 which compose the head are called the skull, which 

 comprehends the bones of the cranium and face, 

 twenty-two in number, in which enumeration the 

 teeth are not included. Some of the bones are in 

 pairs, and others are only single bones. The adult 

 cranium, strictly so called, only consists of eight 

 bones. These are the os frontis, or frontal bone, 

 (Plate HI. fig. 1. No. 1.) which forms the forehead 

 part of the temples, and the roof of the orbits, and its 

 shape has been compared to a cockle or clam shell. 



The os frontis is very smooth, and convex ex- 

 ternally where it forms the forehead, but below, 

 where it assists in forming the orbit, it affords se- 

 Teral processes and cavities. Its inner surface is 

 concave, and is turned towards the brain, and in 

 the centre of its inferior part is the ethmoid bone, 

 which is placed at the top of the cavity of the 

 nostrils. It sometimes consists of two portions, 

 in consequence of the saggital suture being con- 

 tinued down through its middle, to the nose. 

 This, however, is more frequent in females than in 

 males. 



There are several well marked processes, or 

 eminences, both external and internal, the most im- 

 portant of which are the two frontal eminences, 

 which mark the centre of ossification ; two fronta. 

 tuberosities, situated over the frontal sinuses, and 

 two superciliary ridges, or arches, which give origin 

 to the frontal muscles, and whose extremities are 

 called the angular or orbitar processes, and behind 

 such external angular processes the surface of the 

 bone is considerably depressed for the situation of 

 a part of the temporal muscle. There is, like- 

 wise, an external frontal spine, upon which the 

 ossa nasi rest, an internal frontal spine, to which 

 the dura mater adheres, and two orbitav plates 

 which separate the orbits from the cavity of the 

 cranium. 



This bone, which constitutes the forehead, the 

 pituitary, or frontal sinuses part of the orbit, and 

 contains and defends the anterior lobe of the 

 brain, is joined or connected, above or behind, with 

 the ossa parietalia, which junction terminates at 

 a line running horizontally backwards, from the 

 point of the angular process, between these two 

 points, and behind as far as the ethmoid notch ; it 

 joins with the sphenoid bone on each side within the 

 ethmoid notch ; it receives the ethmoid bone, which 

 joins to the orbitar plates, at the inferior part of 

 which it unites with the ossa lachrymalia; in front it 

 joins its nasal process and spine with the ossa nasi 

 and ethmoid bone, and with its outer angular pro- 

 cesses with the malar hones. 



In this bone there are several well defined hol- 

 lows, or cavities, and holes, or foramina, which all 

 serve either to lodge important organs, or afford a 

 passage for blood vessels, nerves, &c. 



One of the most interesting of these are the 

 frontal or pituitary sinuses, or cavities, within the 

 bone above the root of the nose ; they are separated 

 by a thin bony partition, and open, by two small 

 holes, into the nostrils, of which they form a part, 

 and their internal lining is frequently thickened 

 and inflamed in cases of common cold, along 

 with the internal lining of the nasal cavity, and 

 produces that stuffing and dryness of the parts 

 which is so very disagreeable, a symptom when 

 suffering from the effects of cold. It is indispen- 

 sibly necessary for the surgeon to be well acquaint- 

 ed with these sinuses, and with others not less im- 

 portant in this bone, especially that of the dura 

 mater, as they should be cautiously avoided when 

 performing the operation of trepanning. Substances 

 have been forced immediately over the internal 

 angle of the orbit, some way into the skull, and 

 never produced any symptoms common to injuries 

 of the bruin, and whe,n removed it has been ascer- 

 tained that these substances were in the frontal 

 sinuses. 



There are three pairs of muscles attached to the 

 os frontis, viz. the temporal, corrvgator supercilii, 

 and orbicularis palpebrarum ; it is also covered by 

 the occipito frontalis. In the new born infant, the 

 os frontis consists of two portions. The super- 

 ciliary arches and orbitar plates are distinctly 

 formed, and sometimes the frontal sinuses. 



Ossa parietalia, or parietal bones, (Plate III. fig. 

 2. No. 1.) This pair of bones forms the sides and ver- 

 tex, or top of the head, and are joined by their frontal 

 edge to the os frontis, by the parietal edge to its fel- 

 low, by its occipital edge to the os occipitis, and by 

 the tempero sphenoidal edge to the temporal and 

 sphenoid bones. The parietal bones form the supe- 

 rior part of the cranium, and have several eminen- 



