NATURE OF PROTOPLASMIC RESPIRATION. 337 



Whatever their composition may be the active particles attack 

 the water of the protoplasm, oxidize themselves to aldehydes and 

 set free nascent hydrogen. 



R CH < -i- OH 2 = R CHO + zH. 



This explains the presence of aldehydes in protoplasm ; the 

 production of hydrogen by many or all forms of protoplasm as 

 assumed by Hoppe-Seyler and the keeping of the cell protoplasm 

 in a reduced state. It is perfectly clear that surrounded by 

 oxygen as most protoplasm is it could not possibly continue in 

 its reduced condition if some strong reducing agent such as 

 hydrogen was not constantly produced. If too much free oxy- 

 gen is present the aldehydes will be converted into acids, the 

 reaction of the protoplasm changed and the life of the cell 

 destroyed. Oxygen in other words above a certain pressure is 

 poisonous for protoplasm. 



In those forms of protoplasm called anaerobic the active par- 

 ticles are of such a character and so powerful that in the absence 

 of oxygen they can like sodium, oxidize themselves and set free 

 hydrogen ; or in the presence of certain foods which will com- 

 bine with hydrogen such as levulose, they are able to oxidize 

 themselves. In those forms of protoplasm called aerobic the 

 active particles are not so powerful and require the aid of atmos- 

 pheric oxygen to combine with the hydrogen before they can 

 decompose water. While the active particles are formed spon- 

 taneously, the conditions in protoplasm may be such as to accel- 

 erate their formation (ferment action, see Nef). 



A few examples will perhaps make clear the possible relations 

 of this fundamental reaction to the synthetic properties of the 

 protoplasm. The fundamental nature of most of these syntheses 

 is simple and consists in the elimination of water between two 

 simple molecules to form a complex molecule, as for example, 

 in the condensation of the amino acids to form albumin ; of the 

 monosaccharids to form disaccharids and polysaccharids ; of the 

 amino acids to form pyrimidin ; of the alcohols and fatty acids 

 to form fats ; of ammonia and oxyacids to form amino acids. 



Two explanations of this process may be given. That of 

 Drechsel is the first. According to this theory the elements to 



