TECHNICAL USE OF TERMS 3 



nected with the nasal passages; these are cavities in the cranial 

 and facial bones. Lymph sinuses are the spaces within lymph 

 glands. They contain lymph (in some glands blood}. Sinuses 

 containing fluid are large channels in the outer membrane of the 

 brain containing venous blood. Other blood sinuses are found in 

 the heart. The sinus of the kidney is the hollow which is reached 

 through the hilum which leads into it; this contains urine. In 

 surgery a sinus is a narrow abnormal channel through the 

 tissues (usually lined by or connected with an ulcerating surface). 

 Center and periphery are so used (technically) in connection 

 with the nervous system. The center is the cell or cells to which 

 a nerve must belong and be connected with in order to be active. 

 It need not necessarily be in the middle of a part some of the 

 most important centers are on the surface of the brain. The 

 periphery is the location of the extremity of the nerve. Literally 

 it signifies the outer boundary or the outside of a thing, but when 

 used in connection with a nerve it refers to the end farthest from 

 the cell or center, whether within or without the body. 



Centrifugal nerves transmit from center to periphery (they are efferent). 

 Centripetal nerves transmit from periphery to center (they are afferent). 

 Efferent vessels carry blood from organs; afferent vessels carry blood to 

 organs. 



Stimulus in physiology signifies any agency which causes a 

 tissue or an organ to .perform its function. A natural stimulus is a 

 'normal exciting cause and leads to normal action or function. 



An element is, in chemistry, a substance which cannot be 

 divided into other substances. The most important elements in 

 the human body are comparatively few. They will be referred to, 

 sometimes by name, sometimes by symbol. By agreement, 

 certain letters stand for certain elements (usually the initials of 

 their Latin names). 



is the symbol for Oxygen 



H is the symbol for Hydrogen 



N is the symbol for Nitrogen 



C is the symbol for Carbon 



S is the symbol for Sulphur 



Fe is the symbol for Iron (Ferrum) 



P is the symbol for Phosphorus 



K is the symbol for Potassium (Kalium) 



Na is the symbol for Sodium (Natrium) 



