82 IMMUNOLOGY 



Pyelonephritis. — In a like manner anytliing which prevents 

 the normal function of tlie ureters as conductors of urine from 

 the kidney to the bladder will result sooner or later in damming 

 back the urine into the pelvis of the kidney and tlie development of 

 a pyelonephriiis. This may be unilateral or biUiteral. When the 

 latter occurs, uremic complications are possi))le. Cord changes 

 such as are seen in multiple sclerosis and certain types of syphilis 

 can cause paralysis of both ureters. 



Stone in the ureter or kinks due to any one of many causes 

 are commonly responsible for ureteral insufficiency and the prep- 

 aration of a proper "soil" for tlie growtli of infectious agents. 

 These latter may come from the blood stream through the kidney 

 or by some other route. 



Acute Nephritis. — Acute infections of tlie upper respiratory 

 tract are sometimes followed by inflammation of the glomeruli of 

 the kidney (acute glomerular nephritis) as well as infections of 

 the heart or other tissues of the body. It is obviously quite serious 

 for the genitourinary system, heart, central nervous system, or 

 lungs to be impaired by acute infections. In fact, there are many 

 delicate mechanisms that are of great importance in enabling the 

 organism, as a whole, to maintain life in the presence of severe 

 infections. 



Importance of Elimination. — Clinical experience has shown 

 the great importance and imperative necessity of maintaining 

 elimination by kidney, bowel, skin, and lung. It lias also shown 

 that confined pus disturbs the pliysiological balances in the body 

 and that drainage or removal of such products of suppuration 

 is necessary for recovery. 



Mechanical Factors of Safety.— Mel tzer (1906-07) called atten- 

 tion to many mechanical factors of safety in the animal organism. 

 A large amount of lung, liver, and kidney may be rendered func- 

 tionless or destroyed by infection or the spleen may be entirely 

 removed without fatal termination. Undoubtedly there are many 

 more islands of Langerhans present in the pancreas than are needed 

 for adequate insulin production. There is also more thyroid, 

 ovarian, testicular, or adrenal tissue than is necessary for minimum 

 requirements of the individual. 



Physiological Mechanisms. — Some of the physiological mecha- 

 nisms that are important in resistance to infection are those 



