126 



AGRICULTURAL CHEMISTRY. 



But in a child this normal condition of 

 sustenance is accompanied by an abnormal 

 condition of growth and increase in the size 

 of the body, and of each individual part of 

 it. Hence there must be a much larger 

 quantity of foreign substances, not belong- 

 ing to the organism, diffused through every 

 part of the blood in the body of a young 

 individual. 



When the organs of secretion are in pro- 

 per action, these substances will be re- 

 moved from the system ; but when the func- 

 tions of those organs are impeded, they will 

 remain in the blood or become accumulated 

 in particular parts of the body. The skin, 

 lungs, and other organs, assume the func- 

 tions of the diseased secreting organs, and 

 the accumulated substances are eliminated 

 by them. If, when thus exhaled, these sub- 

 stances happen to be in the state of progres- 

 sive transformation, they are contagious; 

 that is, they are able to produce the same 

 state of disease in another healthy organism, 

 provided the latter organism is susceptible 

 of their action or in other words, contains 

 a matter capable of suffering the same pro- 

 cess of decomposition. 



The production of matters of this kind, 

 which render the body susceptible of conta- 

 gion, may be occasioned by the manner of 

 living, or by the nutriment taken by an in- 

 dividual. A superabundance of strong and 

 otherwise wholesome food may produce 

 them, as well as a deficiency of nutriment, 

 uncleanliness, or even the use of decayed 

 substances as food. 



All these conditions for contagion must be 

 considered as accidental. Their formation 

 and accumulation in the body may be pre- 

 vented, and they may even be removed from 

 it without disturbing its most important 

 functions of health. Their presence is not 

 necessary to life. 



The action, as well as the generation of 

 the matter of contagion is, according to this 

 view, a chemical process participated in by 

 all substances in the living body, and by all 

 the constituents of those organs in which 

 the vital principle does not overcome the 

 chemical action. The contagion, accord- 

 ingly, either spreads itself over every part 

 of the body, or is confined particularly to 

 certain organs, that is, the disease attacks 

 all the organs or only a few of them, ac- 

 cording to the feebleness or intensity of their 

 resistance. 



In the abstract chemical sense, reproduc- 

 tion of a contagion depends upon the pre- 

 sence of two substances, one of which be- 

 comes completely decomposed, but commu- 

 nicates its own state of transformation to 

 the second. The second substance thus 



of sulphuric acid, prove that peculiar substances 

 arc contained in the blood of different individuals ; 

 the blood of a man of a fair complexion and that 

 of a man of dark complexion were found to yield 

 different odours ; the blood of animals also dif- 

 fered in this respect very perceptibly from that of 



thrown into a state of decomposition is the 

 newly-formed contagion. 



The second substance must have been 

 originally a constituent of the blood : the 

 first may be a body accidentally present; 

 but it may also be a matter necessary to life. 

 If both be constituents indispensable for the 

 support of the vital functions of certain 

 principal organs, death is the consequence 

 of their transformation. But if the abronoe 

 of the one substance which was a constitu- 

 ent of the blood do not cause an immediate 

 cessation of the functions of the most im- 

 portant organs, if they continue in their 

 action, although in an abnormal condition, 

 convalescence ensues. In this case the pro- 

 ducts of the transformations still existing in 

 the blood are used for assimilation and at 

 this period secretions of a peculiar nature 

 are produced. 



When the constituent removed from the 

 blood is a product of an unnatural manner 

 of living, or when its formation takes place 

 only at a certain age, the susceptibility of 

 contagion ceases upon its disappearance. 



The effects of vaccine matter indicate that 

 an accidental constitution of the blood is 

 destroyed by a peculiar process of decom- 

 position, which does not affect the other 

 constituents of the circulating fluid. 



If the manner in which the precipitated 

 yeast of Bavarian beer acts (page 107) be 

 called to mind, the modus operandi of vac- 

 cine lymph can scarcely be matter of doubt. 



Both the kind of yeast here referred to 

 and the ordinary ferment are formed from 

 gluten, just as the vaccine virus and the 

 matter of small pox are produced from the 

 blood. Ordinary yeast and the virus of 

 human small-pox, however, effect a violent 

 tumultuous transformation, the former in 

 vegetable juices, the latter in blood, in both 

 of which fluids respectively their constitu- 

 ents are contained, and they are reproduced 

 from these fluids with all their charac- 

 teristic properties. The precipitated yeast 

 of Bavarian beer on the other hand acts en- 

 tirely upon the sugar of the fermenting 

 liquid and occasions a very protracted de- 

 composition of it, in which the gluten which 

 is also present takes no part. But the air 

 exercises an influence upon the latter sub- 

 stance, and causes it to alssume a new form 

 and nature, in consequence of which this 

 kind of yeast also is reproduced. 



The action of the virus of cow-pox is 

 analogous to that of the low yeast; it com- 

 municates its own state of decomposition to 

 a matter in the blood, and from a second 

 matter is itself regenerated, but by a totally 

 different mode of* decomposition; the pro- 

 duct possesses the mild form, and all the 

 properties of the lymph of cow-pox. 



The susceptibility of infection by the virus 

 of human small-pox must cease after vacci- 

 nation, for the substance to the presence of 

 which this susceptibility is owing has been 

 remoi ed from the body by a peculiar pro- 

 cess of decomposition artificially excited. 



