■l66 the history of biology 



of the air which is consumed by respiration and that it is substituted in the 

 lungs for carbonic acid. He saw chemical processes both in respiration and 

 in animal heat, as also in fermentation. His influence on the development of 

 science can scarcely be too highly estimated; through him chemistry was 

 led into entirely new channels; through the discovery that oxygen was a 

 constituent common to a mass of chemical elements, the latter could be 

 viewed from a common standpoint and could be given a nomenclature 

 which in part is still in use today. Moreover, to natural science in general 

 these discoveries meant a complete revolution, as they paved the way for 

 the knowledge of the indestructibility of matter. Lavoisier's association 

 with biology lies, of course, mostly in his knowledge of the respiratory 

 process. It was vegetable physiology in particular that felt the immediate 

 influence of the new advance in chemistry. Two examples of this are given 

 in the following. 



Jan Ingenhousz was born at Breda, in Holland, in 1730, and studied 

 medicine at Leyden under Albinus. As a medical practitioner he was espe- 

 cially known for his skill in smallpox inoculation — an operation which in 

 those days was not unaccompanied by danger. Persons of high rank came to 

 him to be inoculated, and he was the recipient of distinguished and high 

 marks of appreciation. He died during a journey lo England in the year 

 1799. In the course of a previous visit to England Ingenhousz had learnt of 

 Priestley's above-mentioned attempts to "improve polluted air" by the in- 

 troduction of live plants, and he resolved to proceed with them in a more 

 extensive and systematic form. And in spite of the fact that his experimental 

 apparatus lacked variety and originality — he immersed different parts of 

 plants in water and collected the gas thus given off by them — he succeeded 

 in establishing a number of facts of fundamental importance for the knowl- 

 edge of plant life. He found that the production of " dephlogisticated air," 

 which constitutes the plant's role as an air-purifier, is a prerogative of the 

 leaves, and particularly of their under side, and that it is brought about 

 exclusively by the influence of sunlight on the plant, whereas during the 

 night, and even in the shadow by day, a kind of air is produced that is 

 fatal to animal life, and that this air is produced by roots, flowers, and fruit, 

 while these latter, if enclosed in a confined air-space, render it impossible 

 for a light to burn in it. Ingenhousz also carried out quantitative investi- 

 gations, though of a somewhat primitive nature. In this field both he and 

 every one of his contemporaries were far outrivalled by a younger scientist, 

 who, it is true, had the inestimable advantage of being able to avail himself 

 of Lavoisier's new methods. 



Nicolas Theodore de Saussure was born at Geneva in 1767. His father 

 was 3 scientist of repute and was interested in botany, but his real mefier 

 was geology. The son also eventually became professor of geology, after- 



