DISEASES OF THE KIDNEY. 515 



3. Disease of the secreting epithelium. This constitutes 

 another element of Blight's disease. The diseased cells fail in 

 function, choke up the tubules, press upon the venous plexus, 

 and thus give rise at once to stagnation of the blood current and 

 resistance to the filtration of water through the glomerulus. The 

 clinical phenomena of this condition (commonly called the Large 

 White Kidney), are very definite. The urine falls in volume; 

 the solids are absolutely diminished, but relatively increased, 

 so that the specific gravity is high ; and in their place there appear 

 albumen, probably derived directly from the venous plexus, 

 blood from the same source or from the glomeruli, and casts 

 formed of diseased cells, fibrin, etc. The blood becomes poisoned 

 by retention of urea. The systemic vessels become diseased, 

 and the heart hypertrophied ; and the blood-change and cardio- 

 vascular disease together lead to marked breathlessness, and to 

 escape of the watery parts of the blood into the tissues and 

 serous cavities, constituting renal dropsy. 



4. Rise of pressure within the uriniferous tubules is a serious 

 cause of complete arrest of the secretion. This is one of the 

 effects of fulness of the venous plexus, and of epithelial ac- 

 cumulations in the tubes, already noticed ; and may also 

 originate in obstruction of the ureter, disease or injury of 

 the bladder and prostate, or stricture of the urethra. 



5. The condition of the blood. This is the most common of all 

 the causes of derangement of the urinary secretion. A number 

 of the disorders of the urine, as regards its reaction and relative 

 composition, can be traced to dyspepsia, hepatic derangement, and 

 defective oxygenation or metabolism ; and even albumen, sugar, 

 and bile may find their way into the urine from the same 

 causes. One striking disorder of the urine is characterised by 

 unnatural alkalinity and by its effects in precipitating the solid 

 constituents. The urine is turbid from precipitation of phos- 

 phates, carbonates, and urates ; and these are deposited in the 

 passages, causing pain and irritation. If the natural acidity of 

 the urine between meals be insufficient to dissolve these alka- 

 line deposits, concretions are formed, and grow at each period 

 of indigestion, until they form a calculus, which may travel down- 

 wards and be expelled with the urine after great s'uffering. 



A similar disorder of the urine is characterised by exces- 

 sive acidity. This has different causal relations, but the 

 ultimate effects are practically the same the precipitation of 

 uric acid and urates, and possibly the formation of calculus. 

 Excessive acidity is chiefly met with in the subjects of disorder 

 of the liver from indulgence in proteid food (see page 443) ; 

 and may be accompanied by an excess of urea, diminution 

 of water, and occasionally by traces of albumen and sugar. 



