Chap. II] 



DEFINITIONS 



17 



The Median Line. — This refers to an imaginary line drawn 

 through the middle of the body, from the top of the head to the 

 middle of the floor between the feet, The parts nearest this line 

 are described as medial, the parts farthest 

 from this line are described as lateral. 



Internal and External. — These terms 

 are used to designate within and without 

 the body itself, also within and without 

 the body cavities. 



Proximal and Distal. — Proximal is used 

 to describe a position near the head or 

 source of any part. Distal is used to de- 

 scribe a position distant, or farthest away 

 from the head or source of any part. 



Periphery. — This term is used to de- 

 scribe the circumference of a circle, hence 

 in anatomy it means the part farthest from 

 the centre. 



THE HUMAN BODY 



It is necessary to have the clearest pos- 

 sible conception of the main divisions and -c o t^ 



_ ^ _ hiG. 3. — Diagrammatic 



the positions of the different parts of the Longitudinal Section op 

 11 1 1 11 .1 e jt ,1 THE Trunk AND Head. 1,1, 



body, and we shall therefore outline the the dorsal cavity; a, the 



structure of the body as a whole. It is ^p^"^^ portion ; b. the cra- 

 nial enlargement ; c, c, the 



readily seen that the human body is sep- bodies of the vertebrce form- 

 arable into trunk, head, and limbs; the Te dtLCd ^tSu^ 

 trunk and head are cavities, and contain ties ; 2, 2, the ventral cavity, 



, . , . 1 1 •! 1 subdivided into thoracic 



the internal organs, or viscera,^ while the cavity (d), abdominal cavity 

 limbs are solid, contain no viscera, and ^');,^°^ '^f''' ^f^^*-^ ({[= 



' ' g, the nasal cavity; /(, the 



are merely appendages of the trunk. mouth, or buccal cavity. 



g~i ..' r J.1- -L J rni . i i The alimentary canal (al) is 



Cavities of the body. — ihe trunk and represented running through 



head contain two main cavities, and look- the whole length of the ven- 

 tral cavity. 

 ing at the body from the outside we should 



naturally imagine that these two cavities were the cavity of the 

 head and the cavity of the trunk, respectively. If, however, we di- 

 vide the trunk and head lengthwise into two halves, by cutting 



1 Viscera is the plural of the Latin word viscus, which means an organ ; hence 

 viscera are organs contained within the body cavities. Example : heart, stomach, 

 etc. Each of these may be called a viscus. 

 c 



