2 INTRODUCTION. 



Descriptire Anatomy may be treated of in two methods ; viz., the 

 Sil>^fcmafic and the Tojyographical. 



In the first or Systematic Anatomy, the several organs and paiis of 

 the body are considered in a systematic order, according to their 

 structnre, their connection with each other, and their relation to the 

 purposes of life ; while in the second, or Topographical Anatomy, the 

 parts are described in the order of their position or association in the 

 same region of the body. The first method is best adapted for the 

 elementary and complete study of the structure of organs, the second is 

 more immediately useful in the study of particular regions in their 

 relation to medicine and surgery. The object of the present work 

 being mainly to serve as a guide for systematic study, the topogra])hical 

 details will be included under and combined with the general descrip- 

 tion of organs. 



The anatomical description of any <:>rgan embraces the consideration 

 of its form, size, position, connection and texture ; the whole of these 

 comprising the structure of the organ. The adult or fully formed 

 condition of the liody is commonly assumed as the subject of this 

 description ; but it is obvious that a consideration of the structure of 

 tlie body and its organs in different stages of life is required to render 

 the knowledge of their anatomy complete. The study of the origin and 

 formation of organs in the embryo, known under the names of 

 Enihnjological Ana torn 1/ or Fcctal Dcvdopmonf, to which a separate 

 chapter will be devoted in this work, is of peculiar importance in indi- 

 cating the general relations of organic structure. 



The study of anatomy may be viewed in two different aspects ; 

 viz., the Physiological and the Morphological. In connection with the 

 first, anatomy supplies the materials rehiting to structure from which an 

 explanation is sought of the uses or functions of organs by the 

 physiologist ; and for this purpose the study of Textural Anatomy is of 

 particular service. In connection with the study of Morphology, 

 Descriptive Anatomy investigates and combines the facts relating 

 to structure and relations of organs, from which may be deduced 

 general principles as to the construction of the human body or that of 

 animals. In tlie determination of these general principles, or laws of 

 Morphology, it is necessary to combine the knowledge of the anatomy 

 of animals with that of man, and both of these with the study of 

 development. 



PLAN OF ORGANISATION. 



Vertebrate Type. — The general plan of construction of the 

 human body agrees closely with that which prevails in a certain 

 number of animals, viz., mammals, birds, reptiles, amphibia, and 

 fishes, and is known as the vertebrate type of •organisation. The 

 main feature of that type, and that from which its name is 

 derived, belongs to the internal skeleton, and consists in the exis- 

 tence of a number of bones (or cartilaginous substitutes) termed 

 vertebra3, which extend in a longitudinal series through the whole 

 trunk of the body, and which by their more solid part, termed 

 ccninun or })od\j, are so disposed as to form a pillar or axis, round 

 which the rest of the ])arts are arranged with a certain conformity of 

 structure. At one extremity of this pillar is situated the head, present- 



