312 GREAT MEN OF SCIENCE 



Gay-Lussac and Avagadro, as well as thpse discovered later, 

 often failed in the case of these organic bodies. 



This led to an ever-increasing number of substances con- 

 taining ever-increasing numbers of atoms in the molecule, 

 and of ever-increasing complexity becoming known, and this 

 forms the substance of the sciences of organic and physio- 

 logical chemistry. These substances, all of them compounds 

 of carbon, were in part taken from living creatures, but also 

 in part had gradually been made artificially from their ele- 

 ments without the intervention of life; they were thus as it 

 were imitated from life, and finally many more substances 

 were made, at least of a simple description, than are actually 

 discoverable in plants and animals.^ 



However, the largest molecules and those containing 

 most atoms, which still provide so many questions for 

 chemistry, are always found in living substances; they appear 

 to form that part of the cell most important for life. 



If we thus glance over all that scientific research has dis- 

 covered in detail concerning living things, little of a funda- 

 mentally new description appears. The only new funda- 

 mental fact concerning the nature of living matter is that the 

 very largest molecules, containing an enormous number of 

 atoms, form the seat of life with its wonderful phenomena, 

 which obviously fall, as regards their origin, outside the 

 frame of all our previous investigation of nature. Every- 

 thing else which depends upon these centres of life, and pro- 

 ceeds from them, is more or less comprehensible on the basis 

 of our experience with non-living matter. We recognise that 

 these centres make use, in the most varied way, of all the 

 processes which the physics of matter and of ether have already 



^ A particular example of this, which one often finds put forward as a 

 milestone on the progress of chemistry towards living matter, with ex- 

 clusion of a life force, is the synthesis of urea without the use of urine, 

 which Wohler (a pupil of Berzelius) succeeded in accomplishing in 1828 

 in Berlin. It must be remembered, however, that urea never appears as 

 a carrier of life; it is a waste product of life, and is as dead as carbonic 

 acid or water vapour and all other products of chemistry hitherto made. 



