POISONS, CONTAGIONS, MIASMS. 



117 



been idded. The water has been yielded 

 bv muscular fibre itself, and having dis- 

 solved the sa .t in immediate contact with it, 

 and thereby lost the power of penetrating 

 animal substances, it has on this account 

 separated from the flesh. The water still 

 retained by the flesh contains a proportion- 

 ally small quantity of salt, having that de- 

 gree of dilution at which a saline fluid is 

 capable of penetrating animal substances. 



This property of animal tissues is taken 

 advantage of in domestic economy for the 

 purpose of removing so much water from 

 meat that a sufficient quantity is not left to 

 enable it to enter into putrefaction. 



In respect of this physical property of 

 animal tissues, alcohol resembles the inor- 

 ganic salts. It is incapable of moistening, 

 that is, of penetrating, animal tissues, and 

 possesses such an affinity for water as to 

 extract it from moist substances. 



When a solution of a salt, in a certain de- 

 gree of dilution, is introduced into the sto- 

 mach, it is absorbed ; but a concentrated 

 saline solution, in place of being itself ab- 

 sorbed, extracts water from the organ, and 

 a violent thirst ensues. Some interchange 

 of water and salt takes place in the stomach ; 

 the coats of this viscus yield water to the 

 solution, a part of which having previously 

 become sufficiently diluted, is, on the other 

 hand, absorbed. But the greater part of the 

 concentrated solution of salt remains unab- 

 sorbed, and is not removed by the urinary 

 passages; it consequently enters the intes- 

 tines and intestinal canal, where it causes a 

 dilution of the solid substances deposited 

 there, and thus acts as a purgative. 



Each of the salts just mentioned pos- 

 sesses this purgative action, which depends 

 on a physical property shared by all of 

 them ; but besides this they exercise a me- 

 dicinal action, because every part of the 

 organism with which they cqme in contact 

 absorbs a certain quantity of them. 



The composition of the salts has nothing 

 to do with their purgative action ; it is quite 

 a matter of indifference a" far as the mere 

 production of this action is concerned (not 

 as to its intensity,) whether the base be 

 potash or soda, or in many cases lime and 

 magnesia ; and whether the acid be phos- 

 phoric, sulphuric, nitric, or hydrochloric. 



Besides these salts, the action of which 

 does not depend upon their power of enter- 

 in? into combination with the component ; 

 Darts of the organism, there is a large class 

 of others which, when introduced into the 

 living body, effect changes of a very differ- 

 ent kind, and produce diseases or death, ac- 

 cording to the nature of these changes, with- 

 out effecting a visible lesion of any organs. 



These are the true inorganic poisons, the 

 action of which depends upon their power 

 of forming permanent compounds with the 

 substance of the membranes, and muscular ! 

 fibre. 



Salts of lead, iron bismuth, copper, and 

 mercury, belong to this class. 



When solutions of these salts are treated 

 with a sufficient quantity of albumen, milk, 

 muscular fibre, and animal membranes, they 

 enter into combination with those sub- 

 stances, and lose their own solubility ; while 

 the water in which they were dissolved loses 

 all the salt which it contained. 



The salts of alkaline bases extract water 

 from animal substances ; whilst the salts of 

 the heavy metallic oxides are, on the con- 

 trary, extracted from the water, for they 

 enter into combination with the animal 

 matters. 



Now, when these substances are adminis- 

 tered to an animal, they lose their solubility 

 by entering into combination with the mem- 

 branes, cellular tissue, and muscular fibre; 

 but in very few cases can they reach the 

 blood. All experiments instituted for the 

 purpose of determining whether they pass 

 into the urine have failed to detect them in 

 that secretion. In fact, during their pas- 

 sage through the organism, they come into 

 contact with many substances by which 

 they are retained. 



The action of corrosive sublimate and 

 arsenious acid is very remarkable in this 

 respect. It is known that these substances 

 possess, in an eminent degree, the property 

 of entering into combination with all parts 

 of animal and vegetable bodies, rendering 

 them at the same time insusceptible of decay 

 or putrefaction. Wood and cerebral sub- 

 stance are both bodies whicn undergo change 

 with great rapidity and facility when sub- 

 ject to the influence of air and water ; but 

 if they are digested for some time with ar- 

 senious acid or corrosive sublimate, they 

 may subsequently be exposed to all the in- 

 fluences of the atmosphere without altering 

 in colour or appearance. 



It is farther known that those parts of a 

 body which come in contact with these sub- 

 stances during poisoning, and which there- 

 fore enter into combination with them, do 

 not afterwards putrefy; so that there can be 

 no doubt regarding the cause of their poi- 

 sonous qualities. 



It is obvious that if arsenious acid and 

 corrosive sublimate are not prevented by the 

 vital principle from entering into combina- 

 tion with the component parts of the body, 

 and consequently from rendering them inca- 

 pable of decay and putrefaction, they must 

 deprive the organs of the principal property 

 which appertains to their vital condition, 

 viz. that of suffering and effecting trans- 

 formations ; or, in other words, organic life 

 must be destroyed. If the poisoning is 

 merely superficial, and the quantity of the 

 poison so small that only individual parts 

 of the body which are capable of being re- 

 generated have entered into combination 

 with it, then eschars are produced a phe- 

 nomenon of a secondary kind the com- 

 pounds of the dead tissues with the poison 

 being thrown off by the healthy parts. 

 From these considerations it may readily be 

 inferred that all internal signs of poisoning 



