TEXT-BOOK OF ANATOMY. 
INTRODUCTION. 
ANATOMY is a comprehensive term, which includes several closely related branches 
of study. Primarily it is employed to indicate the study of the several parts 
which build up the body, and the relationship which these present to each other. 
But during the period of its existence the individual exhibits many structural 
changes: its structure is not the same at all stages of its life. The ovum or 
starting-point of every individual is very different from the finished organism as 
represented by the adult, and the series of changes through which the organism 
passes until its structure is perfected and full growth is attained constitute the 
study of development. The general term “development” includes not only the 
various and striking structural changes which occur during the intrauterine life of 
the individual, to the study of which the term embryology is more specially applied, 
but also many growth processes which occur after birth, such as the later stages in 
the ossification and growth of the bones, the eruption of the two series of teeth, the 
adjustment of the vascular system to its new requirements, etc. The actual obser- 
vation of the processes by which the parts of the body are gradually formed, and of 
the structural arrangements by means of which a temporary connection is estab- 
lished between the ovum and the mother, through which an interchange of 
nutritive and other matters between the two takes place, renders embryology one 
of the most interesting of all the departments of anatomy. The term ontogeny is 
also used to denote the development of the individual. There is, however, another 
form of development, slower, but just as certain in its processes, which affects not 
only the individual, but every member of the animal group collectively to which it 
belongs. The theory of descent or evolution leads us to believe that between man 
of the present day and his remote ancestors there is a wide structural gap, which, 
if the geological record were perfect, would be seen to be completely occupied by 
long-lost intermediate forms. In the process of evolution, therefore, structural 
changes have gradually taken place, which have modified the entire race. A more 
or less close or remote blood-relationship links together all the members of the 
animal kingdom. ‘These evolutionary phases constitute the ancestral history or 
phylogeny of the individual. Ontogeny and phylogeny are intertwined in a 
remarkable manner, and present certain extraordinary relationships. In other 
words, the ancestral evolutionary development appears to be so stamped upon an 
individual that it repeats certain of the phylogenetic stages with more or less 
clearness during the process of its own individual development. Thus at an early 
period in the embryology of man we recognise evanescent gill-slits comparable with 
those of a fish, whilst a study of the development of his heart shows that it passes 
if 
