CHAPTER VII 



THE DEVELOPMENT OF KNOWLEDGE OF THE 

 METABOLIC PROCESSES CONTINUED: 

 DIGESTION. THE NATURE OF NUTRITION 



THERE is perhaps no section of the subject of metabolism 

 that was more closely studied, or which attracted the 

 attention of so many investigators, during the later years 

 of the century, than that which is concerned with the 

 digestive changes that bring reserve materials into active 

 use after their period of quiescence. There are few which 

 were attended by better results. The subject embraces 

 almost all the researches into the existence and the activity 

 of the enzymes or unorganized ferments and the relations 

 between fermentations and putrefactions and the ordinary 

 phenomena of nutrition. One of the chief results that was 

 obtained was the elucidation of the relations of digestive 

 and putrefactive bacteria to the processes associated with 

 the digestive ferments, and the proof that all phenomena of 

 fermentation are to be traced to the vital activity of proto- 

 plasm ; while the question of the unicellular or multicellular 

 nature of the organism whose protoplasm is involved, was 

 found to be of very subordinate importance. The distinc- 

 tion between organized and unorganized ferments was 

 shown by the present writer to be unnecessary 



At the beginning of the period the researches of Pasteur 

 were throwing a flood of light upon many of the vital 

 processes of the lower organisms, and opinion was tending 

 towards the recognition of a close relationship between the 

 phenomena of fermentation and these digestive changes 



