EVOLUTION OF COLLOIDS 153 



that fat might be carried in the tissues in 

 invisible, apparently soluble form in union 

 with the colloidal proteins. The carriage of 

 fat about the body was long a puzzle to the 

 physiologist, for it is insoluble in aqueous 

 solutions, and hence ought to have been 

 easily traced, but its appearances and dis- 

 appearances in many tissues without being seen 

 in transit, formed a perplexing conundrum. 

 Recent work on fatty changes and degenera- 

 tions has demonstrated the exact truth of 

 Graham's remark made a generation earlier. 

 In our present concepts, the colloid of the cell 

 possesses both fat and carbohydrate dissolved 

 and united to protein, and forming a mobile 

 colloidal whole, in which chemical oscillations 

 are ever occurring and new products being 

 elaborated. Carbohydrate and fat are equally 

 indispensable with protein for the maintenance 

 of life. If absent from the food they are 

 manufactured from amino acids by the living 

 complex of the cell. 



Graham also points out that just as ferments 

 during digestion disrupt and dissolve proteins, 

 such as white of egg, so alkali dissolves gela- 

 tinized silica acid, by disrupting the colloidal 

 union of its aggregates, and he calls his gela- 

 tinized colloids pectized colloids, and their 

 process of solution " peptization," on account 



