500 DEFENSES AGAINST DISEASE 



When bacteria actually enter the body and get into the blood 

 or lymph stream, there are many methods of protection. The 



Opsonio InStey Determination. 



'bacteria* 

 serccm (control) "normal serum. 



corpuscles >rhite corptcscles 



^ Q < percentage corpuscles f\A 

 ^O ingesting bacteria > At 



48 



= 2 patient's opsonic index 



Opsonins affect bacteria so that white corpuscles can more easily engulf them. Definite op- 

 sonic indexes may be calculated from microscopic examinations. A pipette, marked as shown 

 in the diagram, is used to measure the amounts of bacteria in the patient's serum and white 

 corpuscles used in the test. 



white corpuscles devour bacteria and digest them. Thus, the body 

 is rid of them. If numbers of bacteria get into the lymph system, 

 they are frequently carried to a lymph node or gland, where the 

 bacteria are filtered out. Then a collection of corpuscles attack 

 the invading germs and destroy them. When a number of 

 tuberculosis germs are combating white corpuscles in a lymph 

 gland, the body sometimes deposits a wall of calcium around the 

 infected center. This removes the whole mass of infected material 

 from the circulation. Infected lymph glands are sometimes cut 

 out of the body to prevent a possible reinfection from the tuber- 

 culosis germs inclosed. 



The type of white corpuscle that devours bacteria is the 

 phagocyte. When germs invade the body, there is an increase 

 in the number of phagocytes produced in order to check the in- 

 fection. If blood is examined, and the number of white cor- 

 puscles is very great, this may indicate an infection in the body. 



