PRODUCTS, ADVENTITIOUS. 



73 



v as exhibited in the annexed table), those of 

 NON-PLASTIC and PLASTIC compounds. The 

 class of non-plastic compounds includes those 

 formed of matter chemically inorganic, and 

 also those which, though organic in a chemical 

 point of view and animalized,yetare completely 

 destitute of structure (for example, animal 

 sugar, cystin, xanthin), and, consequently, in 

 respect of physiological attributes, almost take 

 rank with minerals. The class of plastic com- 

 pounds comprehends all such as present in any 

 degree, be it ever so rudimentary, the characters 

 of structure. A distinction so broad as the 

 absence or presence of structure might, a priori, 

 be affirmed to form a natural basis of classifi- 

 cation; and, as will be seen, products belong- 

 ing to the two classes do absolutely differ in 

 all essential particulars of their physiology and 

 pathology. 



CLASS I. NON-PLASTIC PRODUCTS. 



Products of this class are composed of ma- 

 terials either (first) completely inorganic ; or 

 (secondly) of elements, though organic, inca- 

 pable of assuming organized arrangement ; or 

 (thirdly) they are formed of a union of sub- 

 stances of both these kinds. Of the first va- 

 riety one of the most unquestionable examples 

 is supplied by solid accumulations of calcareous 

 salts round inorganic bodies introduced into 

 the system from without. To the scond be- 

 long biliary calculi, masses composed mainly 

 of an animal substance not only unfitted to 

 form structure, but lowered in the scale of 

 animal existences by having a crystalline form 

 impressed on it. Among the products belong- 

 ing to the third variety may be found, for 

 example, certain urinary calculi, compounds of 

 inorganic saline, and structureless animal, sub- 

 stances. 



All non-plastic products agree in being di- 

 rectly derived from the fluids of the body. But 

 they are not all developed on a uniform plan. 

 Some of them originate in the coalescence of 

 the more solid particles of secreted fluids, 

 after the act of secretion is accomplished ; and 

 this coalescence is essentially a physico- 

 chemical process, primarily, of precipitation, 

 and, secondarily, either of crystallization or 

 accretion. Others are exuded ready formed 

 from the vessels. And this difference in mode 

 of origin coincides with numerous differences 

 in pathological relations; hence it may be ad- 

 vantageously used in forming two sub-classes 

 of non-plastic products ; those 

 (Sub-Class I.) : Produced by precipitation 



from secreted fluids. 

 (Sub-Class II.) : Exuded ready formed from 



the vessels. 



SUB-CLASS I. SALINE PRECIPITATES. 



The various secreted fluids may be regarded 

 as saline solutions, in which the proportion of 

 menstruum and of dissolved salts is chemically 

 accurate. If any cause affect this proportion 

 in such manner as to lower the ratio of solvent 

 fluid, precipitation of the solid matter must 

 follow; or if some new substance be introduced 



which changes the chemical relations of the 

 dissolved and dissolving materials, a similar 

 result necessarily ensues. The alteration of 

 ratio referred to may obviously arise either from 

 diminution of the solvent, or increase of the 

 solid, material. Thelatter of these states exists 

 at the moment of secretion ; the former may 

 either exist then, or be induced subsequently 

 to the act of secretion (in consequence generally 

 of unnatural stagnation of the fluid in its ex- 

 cretory passages) by evaporation, by absorp- 

 tion, possibly by exosmosis, and other agencies. 



But embracing in one view all the saline 

 products found in the body, nothing can be 

 more certain than that a primary modification 

 in the qualities of the secretions themselves is 

 the main agent in their generation. No point 

 in general pathology affords matter of more 

 curious inquiry than the causation of these 

 changes in the character of the secretions. If 

 in some cases observation teaches us to refer 

 them to a local morbid power, limited in dura- 

 tion as in the extent of surface it implicates, 

 in other and much more numerous instances 

 they may be traced to the operation of a con- 

 stitutional influence, itself dependent on diet, 

 mode of life, climate, &c. 



Products belonging to this sub-class present 

 themselves in the form of 



1. Crystalline or amorphous particles ; 

 2. Masses. 



1. Crystalline or amorphous particles. Al- 

 though in the great majority of cases these 

 particles are, as just explained, simple inor- 

 ganic precipitates from the secretions, yet recent 

 inquiries have distinctly shown that they are 

 in some instances associated with organic mat- 

 ter, which retains the form of the saline parti- 

 cles after these have been dissolved away by 

 acids. Now in respect of the mode of associa- 

 tion of the inorganic and organic materials 

 under these circumstances, there are three 

 possible cases. (1.) The organic matter may 

 simply adhere to the surface of the saline in- 

 gredients. (2.) Salts of crystalline form may 

 lie in the interior of an organic cell, closely 

 embraced by its wall. Otoliths are each of 

 them, as shown by Krieger*, enclosed in a 

 membranous vesicle. (3.) What appears to 

 be the crystalline form of the saline matter 

 may, in truth, be simply an accidental result of 

 its association with organic particles, to which 

 the form observed in reality belongs. 



Crystallisation of inorganic matter arises in 

 the human body under various conditions, 

 either after death or during life ; and in the 

 latter case as a natural occurrence, or as a 

 morbid phenomenon. Crystals of these kinds 

 are microscopical objects. 



The fasces contain crystals naturally ; in ty- 

 phoid fever with morbid change in Peyer's 

 glands, crystals appear to form in much greater 

 abundance than under any other circum- 

 stances : in this disease, too, they are found 

 heaped up near the implicated glands, instead 

 of being scattered through the contents of the 

 bowel ; and are said, unlike those of ordinary 



* De Otolithis, p. 15. 



