340 DISEASES OF THE URINARY APPARATUS. 



and by a lessening of the pressure of filtration in the glomeruli. 

 It is probable that there is here, in addition, an intervention of 

 troubles of nutrition and physiological functions of the membranes. 

 The diminution of arterial pressure weakens the transudation in 

 the glomeruli and increases consequently the relative quantity of 

 albumin. The urinary stagnation produces an œdema which is 

 more marked than blood stagnation, and, like this, it results in a 

 diminution of the filtrating pressure ; the quantity of albumin is 

 therefore augmented, and again there is albuminuria. 



2. Alterations of the filtering membrane. These are : inflammatory 

 lesions, fatty degeneration, turbid tumefaction, amyloid degenera- 

 tion. These are the principal alterations which may affect the 

 walls of the glomeruli and their epithelial covering. All these 

 morbid processes also favor the passage of albumin in the urine. 

 A small proportion of albumin is added to that derived from the 

 altered or destroyed cells, the largest part of which is dissolved. 



3. Blood alterations. Albuminuria appears as soon as the pro- 

 portion of albumin increases in the blood (through a too active 

 regeneration, accelerated organic metamorphosis, considerable losses 

 by sudation or diarrhea, infusion of white of egg, the setting free 

 of the albumin of the blood-corpuscle, etc.). 



4. Elevation of the tempeimture (fever) produces albuminuria by 

 increasing the relative quantity of albumin filtered and by causing 

 alteration in the membrane of the filter. 



Clinical importance and proof of albuminuria. Albu- 

 minuria was formerly looked upon as a pathological entity, but the 

 preceding considerations show that in general it constitutes but a 

 symptom which is common to the most diverse diseases. Among 

 these we must particularly mention : 



1. Diseases of the kidneys. (Acute and chronic nephritis, fatty 

 and amyloid degeneration). Albuminuria is never wanting in these 

 affections ; it is the result of the greater permeability of the in- 

 flamed tissues. 



2. Febrile and acute infectious diseases. (Influenza, pneumonia, 

 contagious pneumonia, etc.) The causes are : alterations of the 

 renal tissue, troubles of circulation in the kidneys, abnormal com- 

 position of the blood, elevation of the temperature ; these influences 

 act concurrently. 



3. Passive hyperemia of the kidneys. Such are the valvular 

 lesions of the heart, pulmonary emphysema and induration (heaves), 



