DISEASES OF THE URINAHV ORtJAXS. 157 



Rainey, Oril, aiul others fiirnisli the explanation. Tliev not (inly 

 show that a colloid body, like nineiis, albiinien, pus. or l)lo(nl. ileter- 

 niinetl the precipitation or the crystalline s;ilts in the solution, hut 

 they iletermined the preeijntation in the form of o;lol)ules. or spheres, 

 eapable o( developing ity furthei- deposits into caleidi. Heat intensi- 

 fies this action of the colloids, and a colloid in a slate of decomposition 

 is specially active. The presence, therefore, of de\eloping fungi and 

 bacteria nnist be looked upon as active factors in causing calculi. 



In looking, therefore, for the immediate causes of calculi \ve niu.st 

 consider especially all thc\se conditions \vhi<h deteimine the presence 

 of albumen, blood, and excess of mucus, pus, etc., in the urine. Thus 

 diseases of distant organs leading to albuminuria, diseases of the kid- 

 neys and urinary passages causing the escai)c of blood or the forma- 

 tion of mucus or pus, l)ecome direct causes of calculi. Foreign bodies 

 of all kinds in the bladder or kidney have long been known as deter- 

 mining causes of calculi and as forming the central nucleus. This is 

 now explained b}' the fact that these bodies are liable to carry bac- 

 teria into the passages and thus determine decomposition, and they 

 are further liable to irritate the mucous membrane and become envel- 

 oped in a coating of mucus, pus, and perhaps blood. 



The fact that horses, especially on the magnesian limestones, the 

 same distiicts in which they suffer from goitei-. appear to suffer from 

 calculi may be similarly explained. The unknown poison which pro- 

 duces goiter presumably leads to such changes in the blood and urine 

 as will furnish the colloid necessary for precipitation of the urinary 

 salts in the form of calculi. 



CLASSIFICATION' OF URINARY CALCULI. 



The.se have been named according to the place where they are 

 f(»uiid, renal (kidney), ureteric (ureter), vesical (bladder), urethral 

 (urethra), and preputial (sheath, or prepuce). They have been 

 otherwise named according to their most abundant chemical constit- 

 uent, carbonate of lime, oxalate of lime, and phosphate of lime cal- 

 culi. The stones formed of carbonates or phosphates are usually 

 smooth on tlie surface, though they may be molded into the shape of 

 the cavity in which they have been formed; thus those in the pelvis 

 of the kidney may have two or three short branchlike prolongations, 

 while those in the bladder aie nmnd, oval, or i^lightly flattened upon 

 each other. Calculi containing oxalate of lime, on the other hand, 

 have a rough, open, crystalline surface, which has gained for them 

 the name of mulberry calculi, from a supposed resemblance to tliat 

 fruit. These are usually covered witli more or less nnicus or blood, 

 produced by the irritation of the mucous membrane by their rough 



