34 ANATOMY OF THE RABBIT 



maintenance of life processes in the tissues. The composition of 

 the blood varies from time to time according to the individual 

 functions performed. Oxygen and food materials are carried to the 

 tissues. Carbon dioxide and waste materials of other kinds are 

 carried to organs from which they can be excreted. Blood, how- 

 ever, has been shown to vary in composition in different species of 

 animals, and to be chemically homologous in related ones; and it 

 can develop substances conferring immunity to bacterial diseases, 

 which substances also differ in different species and individuals. 



In most tissues there occurs a tissue fluid the amount and 

 character of which differ in different localities. This is derived 

 primarily from the blood by diffusion through the walls of the 

 capillaries. All materials passing between the tissue cells and the 

 blood stream are transmitted through it. It is taken up by the 

 blind beginnings of the lymphatic capillaries within the tissue, 

 within which vessels it is known as lymph. This is eventually 

 poured into veins and thus mixed with the blood. 



The peritoneal, pleural, and pericardial fluids and the synovial 

 fluid in joints are special examples of tissue fluid and the cerebro- 

 spinal fluid also may be so regarded. 



SPECIAL ANATOMY 



Terminology 



In special or descriptive anatomy it is necessary to employ an 

 extensive system of terminology in order that the various structures 

 of the body may be individually designated, classified, and referred 

 to their respective positions. The terms used for this purpose may 

 be classified into four groups, as follows: (1) general terms — 

 those included in the names of parts, but applicable in themselves 

 to similar structures (arteries, nerves, etc.) in various parts of the 

 body; (2) specific terms or names of parts; (3) regional terms — 

 those defining areas (topographic); and (4) terms of orientation. 



The terms of the first three groups will be defined so far as 

 required wherever it seems necessary. The terms of orientation, 

 however, being based on very general relations of the body, are of 

 wider application and understanding of them is essential for any 



