PRODUCTS, ADVENTITIOUS. 



77 



single substance, are termed simple ; of several, 

 compound. When the different materials are 

 applied in successive laminae, the calculus is 

 said to be alternating (y?g. 76) ; when they 

 are irregularly mingled it is called mixed. The 

 relative frequency of the three kinds may be 

 deduced as follows from tables printed by 

 Dr. Prout. Of 1520 calculi there were 



SIMPLE, 709 ; Alternating, 787 ; Mixed 24-. 



The mode of succession of various substances 

 in the formation of alternating calculi (they 

 may consist of two, three, four, or several suc- 

 cessive strata), is pathologically important, and 

 has been specially investigated by Dr. Prout. 

 The nature of this work prevents us from en- 

 tering into the subject, but we may mention (as 

 evidence of the generality of Dr. Front's law, 

 that the existence of mixed phosphates in a 

 calculus excludes the subsequent deposition of 

 other matter), that of 566 alternating calculi 

 composed of two layers, two only were examples 

 of a nucleus of phosphates with a cortex of 

 another kind of salt ; that of 172 calculi formed 

 of three layers, not one had a phosphatic nu- 

 cleus, and in only three was the middle stratum 

 composed of phosphates ; and that, lastly, of 

 25 calculi containing four distinct layers, not 

 one had a nucleus of phosphates ; in one only 

 was the second layer, and in three only was the 

 third layer, thus composed. It is, however, 

 right to observe that if small quantities of 

 phosphates, not forming actual layers, were 

 taken into consideration, the exceptions to the 

 law would be much more numerous. 



The degree of rapidity with which calculi 

 form and acquire bulk depends upon the con- 

 stitutional condition of the individual in whom 

 they form, much more than upon the nature 

 of their own ingredients ; for, if it be true that 

 oxalate of lime and uric acid calculi commonly 

 enlarge slowly, and the phosphatic species 

 with great quickness, instances of the direct 

 contrary are far from uncommon. The cases 

 in which calculous matter accumulates round 

 a foreign body are obviously those, and those 

 alone, in which perfect accuracy as to dates 

 can be obtained ; now cases are on record 

 showing that some weeks suffice in one case 

 for as abundant accumulation of phosphates as 

 several months in another. The slower the 

 enlargement, the greater, cattcris paribus, the 

 density of the mass. In this latter quality 

 calculi vary exceedingly, some being as re- 

 markable for their porousness and openness 

 of texture, as others for their compactness 

 and closeness. Their specific gravity, accord- 

 ing to Fourcrov, varies from 1213 to 1976, 

 water being 1000 ; Scharling found it in one 

 instance to amount to 2014. 



Calculi are commonly solitary ; from some 

 calculations, which have been madeon a limited 

 scale, it would appear, however, that in one of 

 every five or six cases of calculous disease two 

 or more calculi are met with. The number 

 and size of these bodies discovered in the 

 bladder are sometimes almost marvellous ; thus 

 Rodrigue de Fonseca refers to a case in which 

 that viscus contained fifty as hirge as nuts ; fifty- 



nine were found in Buffon's bladder ; and 

 Moraud counted six hundred and seventy-eight 

 in the bladder of an old man, and nearly ten 

 thousand in his kidneys. Probably miliary 

 calculi only accumulate in such extraordinarily 

 great numbers. 



We shall now briefly consider the physical 

 and chemical characters of each calculus in par- 

 ticular, appending in each instance an out- 

 line of the qualities of its component material, 

 when occurring in the form of urinary sediment. 



1. The uric acid calculus is generally of oval 

 shape and somewhat flattened, ranges in weight 

 from a grain to six or seven ounces and up- 

 wards, and varies in size within corresponding 

 limits ; the calculus, from a section of which 

 the subjoined cut is reduced, measures 2-f in- 

 ches in breadth and 3f inches in length. The 



Fig. 77. 



Section of an uric acid calculus. ( Univ. Coll. Museum.) 



external surface, commonly smooth, may be 

 finely granular, and its colour brown of diffe- 

 rent tints and depths, unless it have received 

 a thin coating of phosphates. On section it is 

 generally found to be laminated, and when 

 comparatively pure its fracture has a crystalline 

 look ; when the contrary, the appearance is 

 that of aggregated amorphous particles ; the 

 general colour is that of the external surface 

 (much impurity may, however, render it gray 

 or otherwise alter it), but the different strata 

 may vary very considerably in depth of hue 

 from yellowish-brown to mahogany colour, ac- 

 cording to the amount of colouring matter pre- 

 sent in each ; its density is high in the direct 

 ratio of its purity. Absolute purity never 

 exists ; all uric acid calculi contain colouring, 

 and, with rare exceptions, fatty matters, some 

 mucus or albumen, and besides, minute quan- 

 tities of urate of ammonia, of soda, and of 

 potash, with occasionally carbonate and phos- 

 phate of lime. 



In 251 of the 763 alternating calculi, the 

 composition of which is given by Dr. Prout, 

 the nucleus consisted of uric acid. 



Uric acid occurs as an ingredient of urinary 

 sediments, and although not, as Berzelius sup- 

 posed, their chief material in persons in health, 

 (the amorphous urates vastly exceed it in abun- 

 dance,) it may in cases of gout form the entire 

 of the deposit. 



Under the microscope uric acid appears in 

 the form of semi-transparent, thin rhomboidal 

 scales, of slightly yellow tinge, generally, from 

 impurity (the pure acid being brilliantly white), 



