64 HISTORY OF BOTANY 



curriculum Ingen-Housz took up the practice of medicine, 

 first in Holland and afterwards, about 1764, in England. 

 Four years later he became physician to the Austrian 

 Emperor and resided in Vienna. His tastes seem to 

 have been scientific rather than medical, for during his 

 life in the Austrian capital he began to send papers to 

 the Royal Society of London, of which he was elected a 

 Fellow on his return to England in 1778 or 1779. In the 

 latter year Ingen-Housz pubUshed his Experiments on 

 Vegetables, carried out in his garden near London, in 

 leisure intervals of his professional labours among the 

 dyspeptic attendants at the Court of George III. His 

 discoveries are so important that I must quote them to 

 you rather fully : 



" The discovery of Dr Priestley," he writes, " that 

 plants thrive better in foul air than in dephlogisticated 

 air, and that plants have a power of correcting foul air, 

 has thrown a new and important fight upon the arrange- 

 ments of this world. It shows, even to a demonstration, 

 that the vegetable kingdom is subservient to the animal ; 

 and, vice versa, that the air, spoiled and rendered noxious 

 to animals by their breathing in it, serves to plants as a 

 kind of nourishment." (Priestley speaks of " the pabulum 

 which plants derive even from common air.") " When 

 these observations are well considered, I think it will 

 hardly be doubted but that there is something in the 

 process of vegetation, or at least something usually 

 attending it, that tends to amefiorate the air in which 

 it is carried on, whatever be the proximate cause of this 

 effect, whether it be the plants imbibing the phlogistic 

 matter, as part of their nourishment, or whether the 

 phlogiston unites with the vapour that is continually 

 being exhaled from them ; though of the two opinions 

 I should incfine to the former. The Rev. Dr. Priestley 

 found that water, chiefly pump water, standing some 

 days by itself formed at the bottom and sides of the 

 vessel a kind of green matter, seemingly vegetable, from 



