the oxide formed the cortex of a uric acid nu- 

 cleus ; in the others it was the sole ingredient. 

 Unger has discovered minute traces of a sub- 

 stance which he considers closely allied to, if 

 not identical with, xanthin in guano : its pre- 

 cise chemical relations, however, appear to be 

 as yet not fully determined. 



Observations are wanting concerning the 

 characters of uric oxide sediments : Berzelius 

 says they are pulverulent and grey. 



9. The carbonate of lime calculus, very rare 

 in man, is not uncommon in graminivorous 

 animals. Dr. Prout has seen some small cal- 

 culi from the human subject consisting of this 

 salt, of perfectly white colour and very friable. 

 The carbonate may, however, be impure, and 

 the mass accordingly vary in colour from yel- 

 low to brown and red. this species has been 

 observed by Smith with the appearance of a 

 mulberry calculus*, by Brugnatelli, Fromm- 

 herz, Walther, Loir, and others. Wood f has 

 described two of pearly, and Rampold J one 

 of metallic lustre. 



10. Carbonate of magnesia, according to 

 Berzelius, very probably exists in all calculi 

 composed of carbonate of lime. It appears to 

 have been actually detected in two instances 

 only, once by Moscati, once by Lindbergson. 



11. Urate of magnesia has been found form- 

 ing the chief mass of two calculi by Scharling; 

 urate of ammonia was likewise present. 



1 2. Urates of soda, potassa, and lime, never 

 form the entire mass of a calculus. The former 

 was found in large quantity by Lindbergson in 

 the calculus just referred to. It is uncertain 

 whether urate of soda exists naturally in the 

 urine ; it occurs in association with uric acid 

 and urate of ammonia in sediments, as already 

 mentioned. 



13. Phosphate of magnesia is, according to 

 Brugnatelli, of common occurrence, either 

 mixed with triple phosphate, or forming alter- 

 nate layers with it. 



14. Chloride of sodium never forms the sub- 

 stance of calculi, and the conditions under 

 which this salt crystallizes in the urine are not 

 well ascertained : partial evaporation of the 

 fluid must first take place. The crystals are 

 octahedral, and have their planes indented 

 like steps of stairs. 



The nature of the so-called fibrinous calcu- 

 lus (originally described by Dr. Marcet) has 

 been made matter of question by Berzelius. 

 It appears that the material supposed to be 

 fibrin by that analyst was soluble, though not 

 readily so, in nitric acid, a character not be- 

 longing to either fibrin or albumen. This, with 

 other of its properties as detailed by Marcet, 

 leads Berzelius to regard the matter as inspis- 

 sated vesical mucus. 



The Museum of University College contains 

 a " fibrinous calculus " taken from the bladder 

 of a cow (Jig. 85). It is of irregular elon- 



PRODUCTS, ADVENTITIOUS. 8l 



brownish grey colour internally, whitish exter- 

 nally, and coated with a white earthy crust. 



Fig. 85. 



gated shape, measuring two and a half by one 

 and a half inches ; very light ; elastic ; of 



* Med. Cbirurg. Trans, vol. ix. p. 14 

 t Med. and Phys. Journ. vol. Ivii. 

 j Schmidt's Jahrbuch, B. v. S. 379. 



VOL. IV. 



Section ofjibrinous calculus. 



A new substance has recently been added 

 to the list of constituents of urinary calculi by 

 Heller*, under the title of urostealith. This 

 substance is said to form a soap with alkalies, 

 and to have been discharged in small masses 

 varying in size from that of a hemp seed to 

 that of a small nut. 



Each particular division of the urinary pas- 

 sages is the seat occasionally of calculous for- 

 mations, and the characters of these are in each 

 site more or less peculiar. Into the description 

 of these characters we cannot here enter seri- 

 atim ; of the varieties thus depending upon the 

 seat of the product namely, renal, ureteral, 

 vesical, prostatic, urethral, and prcBputial, the 

 most important, the vesical, may be considered 

 to have been specially kept in view in the pre- 

 ceding pages. As respects renal calculi we 

 must content ourselves with illustrating by a 

 (Jig. 86) the curious branched form 



figure 



Fig. 86. 



they sometimes assume, as they gradually 

 mould themselves to the interior of the pelvis 

 and infundibula. 



Renal calculi sometimes attain great bulk. 

 Among numerous examples of the fact we 

 may refer to a case seen by Wilson-f-, in which 

 the kidney, perfectly atrophous, and replaced 

 by a multilocular membranous sac (the dilated 

 pelvis and infundibula) contained an oxalate 

 of lime calculus weighing seven ounces and a 

 half. Renal calculi derive much of their prac- 

 tical interest from their tendency to produce 

 such atrophy of the kidney, with pyelilis (U. 

 C. Mus.) or, more rarely, hydronephrosis. 



* In seinem Archiv, Bd. ii. 

 t Lectures, p. 122. 



