124 Chemical Besearches upon Diseased Milk, 



the animal economy which may be found in the atmosphere, 

 in water, &c. or which may result from a change of the 

 equilibrium in the elements which constitute organic sub- 

 stances, whether this change occur in what is called /erwew.'rt- 

 tion, or in the putrefaction of matter which belonged to a liv- 

 ing being, or which may take place in an individual labouring 

 under disease, should be investigated as among the most im- 

 portant researches connected Avith the history of the animal 

 economy. If at the present time the chemist is not called 

 upon to express his sentiments respecting the definitions of 

 the causes to which endemic, epidemic, contagious and infec- 

 tious disorders are attributed ; and if in the physico-chemical 

 sciences, he discovers reasons for studying the influence which 

 the wind and sudden changes of pressure produce, also those 

 Avhich the temperature and humidity of the atmosphere may 

 effect upon the animal frame, these are the strongest possible 

 motives to excite to researches, tending to discover the causes 

 of a disease which is destroying a population, in some dele- 

 terious substance which may be spread throughout the atmo- 

 sphere, or contained in the waters, or in some morbid pro- 

 ducts. He ought not, therefore, to be inclined to adopt the 

 opinion of some individuals who have been in too much haste 

 to conclude affirmatively that there are no such substances, 

 either as deleterious effluvia, miasmata, or noxious virus, be- 

 cause all the researches which have been undertaken to dis- 

 cover their existence have hitherto given only a negative re- 

 sult ; and, on the other hand, where he does discover some 

 particular substance which he suspects had a deleterious in- 

 fluence, and which, on further inquiry, he found had not so 

 in reality, he must, ere his researches are complete, advance 

 to new investigations respecting the animal economy, by em- 

 ploying, not only the matter in question but the products also 

 which he may procure from it, under the influence of air, 

 water, heat, &c. For example, let us suppose that butyric 

 acid was a miasma or poison to some animal, it is evident 

 that were the butter destitute of the acid, it would be innocu- 

 ous to it, and that if, from the action of the atmosphere, or 

 ;iny other cause, it afresh disengaged butyric acid, it would 

 hereby become deleterious. Nothing on this subject is of 



