118 



AGRICULTURAL CHEMISTRY. 



are variable and uncertain ; for cases may 

 happen, in which no apparent indication of 

 change can be detected by simple observa- 

 tions of the parts, because, as has been al- 

 ready remarked, death may occur without 

 the destruction of any organs. 



When arsenious acid is administered in 

 solution, it may enter into the blood. If a 

 vein is exposed and surrounded with a solu- 

 tion of this acid, every blood-globule will 

 combine with it, that is, will become poi- 

 soned. 



The compounds of arsenic, which have 

 not the property of entering into combina- 

 tion witn the tissues of the organism, are 

 without influence on life, even in large doses. 

 Many insoluble basic salts of arsenious acid 

 are known not to be poisonous. The sub- 

 stance called alkargeri, discovered by Bunsen, 

 has not the slightest injurious action upon 

 the organism ; yet it contains a very large 

 quantity of arsenic, and approaches very 

 2-losely in composition to the organic arse- 

 nic :.s compounds found in the body. 



These considerations enable us to fix with 

 tolerable certainty the limit at which the 

 above substances cease to act as poisons. 

 For since their combination with organic 

 matters must be regulated by chemical laws, 

 death will inevitably result, when the organ 

 in contact with the poison finds sufficient 

 of it to unite with atom for atom ; whilst if 

 the poison is present in smaller quantity, a 

 part of the organ will retain its vital func- 

 tions. 



According to the experiments of Mulder,* 

 the equivalent in which fibrin combines with 

 muriatic acid, and with the oxides of lead 

 and copper, is expressed by the number 6361. 

 It may be assumed therefore approxima- 

 tively, that a quantity of fibrin correspond- 

 ing to the number '6361 combines with 1 

 equivalent of arsenious acid, or 1 equiva- 

 lent of corrosive sublimate. 



When 6361 parts of anhydrous tinrm are 

 combined with 30,000 parts of waier, it is 

 in the state in which it is contained in mus- 

 cular fibre or blood in the human body. 

 100 , Ams of fibrin in this condition would 

 form a neutral compound of equal equiva- 

 lents with 3 T ^ grains of arsenious acid, and 

 5 grains of corrosive sublimate. 



The atomic weight of the albumen of 

 eggs and of the blood deduced from the 

 analysis of the compound which it forms 

 with oxide of silver is 7447, and that of 

 animal gelatin 5652. 



100 grains of albumen containing all the 

 water with which it is combined in the liv- 

 ing body, should consequently combine with 

 l grain of arsenious acid. 



These proportions which may be consi- 

 dered as the highest which can be adopted, 

 indicate the remarkably high atomic weights 

 of animal substances, and at the same time 

 teach us what very small quantities of arse- 



* Poggendorff's Annalen, Band xl. S. 259. 



mous acid or corrosive sublimate are requi- 

 site to produce deadly effects. 



All substances administered as antidotes 

 in cases of poisoning, act by destroying die 

 power which arsenious acid and corrosive 

 sublimate possess, of entering into combi- 

 nation with animal matters, and of thus 

 acting as poisons. Unfortunately no other 

 body surpasses them in that power, and the 

 compounds which they form can only be 

 broken up by affinities so energetic, tha 

 their action is as injurious as that of the 

 above-named poisons themselves. The duty 

 of the physician consists, therefore, in his 

 causing those parts of the poison which 

 may be free and still uncombined, to enter 

 into combination with some other body, so 

 as to produce a compound incapable of 

 being decomposed or digested in the same 

 conditions. Hydrated peroxide of iron is 

 an invaluable substance for this purpose. 



When the action of arsenious acid or 

 corrosive sublimate is confined to the sur- 

 face of an organ, those parts only are de- 

 stroyed which enter into combination with 

 it; an eschar is formed, which is gradually 

 thrown off. 



Soluble salts of silver would be quite as 

 deadly a poison as corrosive sublimate, did 

 not a cause exist in the human body by 

 which their action is prevented, unless their 

 quantity is very great. This cause is the 



Eresence of common salt in all animal 

 quids. Nitrate of silver, it is well known, 

 combines with animal substances, in the 

 same manner as corrosive sublimate, and 

 the compounds formed by both are exactly 

 similar in the character of being incapable 

 of decay or putrefaction. 



When nitrate of silver in a state of solu- 

 tion is applied to skin or muscular fibre, it 

 combines with them instantaneously; ani- 

 mal substances dissolved in any liquid are 

 precipitated by it, and rendered insoluble, 

 or, as it is usually termed, they are coagu- 

 lated. The compounds thus formed are 

 colourless, and so stable, that they cannot 

 be decomposed by other powerful cnemicai 

 agents. They are blackened by exposure to 

 light, like all other compounds of silver, in 

 consequence of a part of the oxide of silver 

 which they contain being reduced to the 

 metallic state. Parts of the body which 

 have united with salts of silver no longer 

 belong to the living organism, for their vital 

 functions have been arrested by combina- 

 tion with oxide of silver ; and if they are 

 capable of being reproduced, the neighbour- 

 ing living structures throw them off in the 

 form of an eschar. 



When nitrate of silver is introduced into 

 the stomach, it meets with common salt and 

 free muriatic acid ; and if its quantity is 

 not too great, it is immediately converted 

 into chloride of silver a substance which 

 is absolutely insoluble in pure water. In a 

 solution of salt or muriatic acid, however, 

 chloride of silver does dissolve in extremely 

 minute quantity; and u is this small par* 



