784 SPECIAL PHYSIOLOGY. 



mus paper is permanent ; whilst with ammoniacal urine, it is fugitive, 

 owing to the volatility of ammonia. The alkaline fermentation is prob- 

 ably induced by the pus, or by the excess of mucus. The acid fer- 

 mentation is also believed to be excited by the mucus of the bladder. 

 The abundant sediments formed in the critical stages of fevers and 

 gout, are of the uric acid type. The fine iridescent film, frequently 

 seen on the surface of the urine, in dyspeptic and nervous diseases, 

 consists of crystals of the triple phosphate of ammonia and magnesia. 

 Prolonged mental effort is said to cause an increase in the amount of 

 phosphates ; but this is not established by observation, although this 

 condition does occur in diseases of the nervous centres. The known 

 existence of phosphorus in the fatty matter of the brain, has doubtless 

 suggested this idea. Other morbid sediments consist of pus and blood. 



The concrete deposits named calculi, commence by the collection of 

 some crystallizable substance, around accidental fibrinous or other 

 masses which may be minute, and ultimately almost or entirely dis- 

 appear. Upon such a centre of formation or nucleus, successive lay- 

 ers of crystallized substance are deposited in laminae or crusts, ce- 

 mented together by traces of mucus. The first layers deposited, often 

 differ from those which follow, and sometimes the layers alternate, 

 constituting a composite calculus. The simplest calculi are those con- 

 sisting of a mixture of uric acid with urates, forming the uric or lithic 

 acid, group', they are generally oval, somewhat flattened, smooth, or 

 slightly rough, yellowish, and hard. The oxalate of lime or mulberry 

 calculi are, as their name implies, roughly tuberculated, and brownish 

 or black in color ; they are very hard. They contain some coloring 

 substance derived from the blood. The phosphatic calculi are either 

 smooth on the surface, opaque- white, or white and semi-transparent, or 

 else finely crystalline, light and soft, so as, indeed, to be easily worn 

 by attrition, when two or more coexist in the bladder ; they offer but 

 little resistance to crushing instruments. They are composed of the 

 triple phosphate of ammonia and magnesia, combined with some phos- 

 phate of lime. Other and rarer forms of urinary concretions, are the 

 carbonate of lime, cystic oxide, and xanthic oxide calculi. 



Many articles of diet and medicinal agents pass into the urine en- 

 tirely unchanged; such are the alkaline chlorides, phosphates, sul- 

 phates, and nitrates. Of these salts, chloride of sodium acts especially 

 as a stimulant to all the processes of tissue metamorphosis, and herein 

 may be found one of the chief uses of this universal constituent in the 

 fluids of all animals. The carbonates of the alkalies, and the caustic 

 alkalies, produce, however, still more powerful effects. The vegetable 

 alkaloids, as quinine, morphia, and strychnia, certain vegetable color- 

 ing substances, such as saffron and rhubarb, and many odorous sub- 

 stances, as turpentine, garlic, assafoetida, and valerian, likewise pass 

 unchanged. Nitric, phosphoric, and sulphuric acids also escape, com- 

 bined with appropriate bases derived from the blood ; sulphuric acid 

 displaces phosphoric and this latter acid, the feebler inorganic and 

 organic acids. Most substances, however, undergo a change before 

 they enter the urine. Thus, the organic acids, such as lactic, but espe- 

 cially tartaric, citric, malic, racemic, and also acetic acid, and their 

 salts, do not reach the urine as such, but, united with soda or potash, 



