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uber die Respiration der Pflanzen. Mimchen, 1850. For accounts of van Helmont's hfe and work: Kopp. H., Geschichte der Chemie. 1843, I, p 117Mevlv f891 p 7Z'°"'^" '''"""^°^Chemistry. Translated by G. McGowan LondonTHE ORIGIN OF ORGANIC MATTER l5 of our knowledge of photosynthesis. Priestley had noticed that plants confined in an atmosphere rich in fixed air (carbon dioxide) produced in the course of several days large quantities of dephlogisticated air (oxygen).Priestley explained the i)henomenon as caused by the growth of the plants. About the same time Scheele, working in Sweden, occupied himself with the same subject. He arrived at results which were quite the opposite to those of Priestley. While Priestley's plants improved the air with oxygen, Scheele's plants produced carbon dioxide. As we now know, the cause of this contradiction lay in the fact that neither Priestley nor Scheele realized clearly under what external conditions the plant emitted carbon dioxide and when it emitted oxygen. Priestley industriously repeated his investigations but became confused through the irregular outcome of his experiments.In 1768 Jean Ingen-Housz, a Dutch physician, who had been studying vaccination against small-pox in London, was called to Vienna to combat this disease which was raging in that city and had claimed many victims from the royal family. Ingen-Housz had wide scientific interests and knowledge. It was through reading the address of Pringle on Priestley's discoveries, which has already been referred to, that Ingen-Housz became filled with the desire to repeat the experiments on the production of oxygen by plants.Through his successes with vaccination he soon won the favor of the Empress Maria Theresa and was finally given an annuity from the state which permitted him to follow his own scientific investigations. Ingen-Housz was at first primarily interested in the influence of foul and pure air on the health of man. The discoveries of Priestley, already referred to, served as a great stimulus to his studies and were the beginning of his fundamental discoveries. Thus, in the preface to his "Experiments upon Vegetables" (1779) he wrote: "The discovery of Dr. Priestley that plants thrive better in foul air than in common and in dephlogisticated air, and that plants have a power of correcting bad air, has thrown a new and important light upon the arrangements of this world. It shews . . -that the air, spoiled and rendered noxious to animals by their breathing in it, serves to plants as a kind of nourishment."Ingen-Housz was much more fortunate in his experimentation than either Priestley or Scheele. He soon saw that the mere growth of a plant had nothing to do with the purification of the air. His experiments are masterpieces of manipulation and self-criticism. It should be remembered that this was before Lavoisier had established the nature of combustion.Step by step Ingen-Housz approached the correct interpretation of the phenomenon. The plants were able to purify bad air in a few hours when subjected to sunlight....

This paper comprises the results of investigations carried out during 1916-1918. The work consisted largely of the analysis of plants which had been subjected to various experimental conditions. Of the large number of analyses made, only those are discussed here which are pertinent to the immediate subject It is a pleasure to acknowledge here the assistance