POISONS, CONTAGIONS, MIASMS. 



129 



organ opposes no resistance. The compo- 

 nent parts of the organ must suffer changes 

 simultaneously with the starch, so that the 

 more starch is furnished to it, the more ener- 

 getic and intense the disease must become ; 

 while if only food which is incapable of 

 suffering such transformations from the 

 same cause is supplied, and the vital energy 

 is strengthened by stimulant remedies and 

 nourishment, the chemical action may finally 

 be subdued, or, in other words, the disease 

 cured. 



The conversion of starch into sugar may 

 also be effected by pure gluten, and by dilute 

 mineral acids. 



From all the preceding facts, we see that 

 very various transpositions, and changes of 

 composition and properties, may be pro- 

 duced in complex organic molecules, by 

 every cause which occasions a disturbance 

 in the attraction of their elements. 



When moist copper is exposed to air con- 

 taining carbonic acid, the contact of this 

 acid increases the affinity of the metal for 

 the oxygen of the air in so great a degree 

 that they combine, and the surface of the 

 copper becomes covered with green carbo- 

 nate of copper. Two bodies, which pos- 

 sess the power of combining together, as- 

 sume, however, opposite electric conditions 

 at the moment at which they come in 

 contact. 



When copper is placed in contact with 

 iron, a peculiar electric condition is excited, 

 in consequence of which the property of 

 the copper to unite with oxygen is destroyed, 

 and the metal remains quite bright. 



When formate of ammonia is exposed to 

 a temperature of 388 F. (180 C.) the in- 

 tensity and direction of the chemical force 

 undergo a change, and the conditions under 

 which the elements of this compound are 

 enabled to remain in the same form ceases 

 to be present. The elements, therefore, ar- 

 range themselves in a new form; hydro- 

 cyanic acid and water being tne result of 

 the change. 



Mechanical motion, friction, or agitation, 

 is sufficient to cause a new disposition of 

 the constituents of fulminating silver and 

 mercury, that is, to effect another arrange- 

 ment of their elements, in consequence of 

 which, new compounds are formed. 



We know that electricity and heat possess 

 a decided influence upon the exercise of 

 chemical affinity; and that the attractions 

 of substances for one another are subordi- 

 nate to numerous causes which change the 

 condition of these substances, by altering 

 the direction of their attractions. In the 

 same manner, therefore, the exercise of 

 chemical powers in the living organism is 

 dependent upon the vital principle. 



The power of elements to unite together, 

 and to form peculiar compounds, which are 

 generated in animals and vegetables, is 

 chemical affinity ; but the cause by which 

 they are prevented from arranging them- 

 selves according to the degrees of their natu- 



ral attractions the cause, therefore, by 

 which they are made to assume their pecu- 

 liar order and form in the body is the vital 

 principle. 



After the removal of the cause which 

 forced their union that is, after the extinc- 

 tion of life most organic atoms retain their 

 condition, form, and nature, only by a vis in- 

 ertia ; for a great law of nature proves that 

 matter does not possess the power of spon- 

 taneous action. A body in motion loses its 

 motion only when a resistance is opposed to 

 it ; and a body at rest cannot be put in mo- 

 tion, or into any action whatever, without 

 the operation of some exterior cause. 



The same numerous causes which are 

 opposed to the formation of complex organic 

 molecules, under ordinary circumstances, 

 occasion their decomposition and transform- 

 ations when the only antagonist power, the 

 vital principle, no longer counteracts the in. . 

 fluence of those causes. Contact with air 

 and the most feeble chemical action now 

 effect changes in the complex molecules ; 

 even the presence of any body the particles 

 of which are undergoing motion or transpo- 

 sition, is often sufficient to destroy their state 

 of rest, and to disturb the statical equilibrium 

 in the attractions of their constituent ele- 

 ments. An immediate consequence of this 

 is that they arrange themselves according to 

 the different degrees of their mutual attrac- 

 tions, and that new compounds are formed 

 in which chemical affinity has the ascend- 

 ency, and opposes any further change, 

 while the conditions under which these 

 compounds were formed remained unaltered. 



TABLES: 



SHOWING THE PROPORTION BETWEEN THE 



HESSIAN AND ENGLISH STANDARD OF 



WEIGHTS AND MEASURES. 



IN general all the weights and measures 

 employed in this edition are those of the 

 English standard. In a few cases only, the 

 Hessian weights and measures have been 

 retained. In these the numbers do not re- 

 present absolute quantities, but are merely 

 intended to denote a proportion to other 

 numbers. This has been done to avoid any 

 unnecessary intricacy in the calculations, 

 and to present whole numbers to the reader, 

 without distracting his attention by decimal 

 parts. For those, however, who wish to be 

 acquainted with the exact English quanti- 

 ties, a table is given below. 



1 Ib. English is equal to 0-90719 Ibs. Hes- 

 sian, hence, about one-tenth less than the 

 latter. 



1 Ib. Hessian is equal to T102 Ibs. English. 



2 Ibs. Hessian are equal to 2'204 " 



3 3-306 " 



4 - - - - 4-409 



5 5-511 " 



6 .... 6-612 " 



7 7-716 " 



8 - 8-818 " 



