24 SCIENCE PROGRESS 



Such objections as I have urged against the lymphocyte 

 hypothesis of assimilation either did not occur to its author 

 or had no weight with him. In 1906 he states the matter 

 dogmatically thus : " Food into lymphocytes, lymphocytes into 

 proteids, proteids into tissue-substance may be taken as repre- 

 senting the chain of physiological connexions between the 

 food and the tissues." 



Later Adjustments in Pavy's Views 



I have spoken above of two preconceptions dominating 

 Pavy's mind. The first, concerning the relations of the blood 

 and the kidneys, has been dealt with ; the second was one 

 which made it possible for him to hold a view such as that 

 just discussed. He was one of those who held that chemical 

 changes in the material of the animal body occur only while 

 such material is in the strictest sense a part of the living 

 complex. The molecules that undergo change are molecules 

 that are in some way alive. Such an assumption involves 

 either a tendency to cease thinking about the phenomenon in 

 terms of structural organic chemistry altogether or a tendency 

 to use loose pseudo-chemical concepts of " living molecules 

 with stable central nuclei and active side-chains." This is not 

 the place to discuss so difficult a question as the chemical 

 constitution of bioplasm but it is important to point out that 

 the encouraging recent progress in biochemistry has been 

 associated with a recognition of the fact that the complex 

 tangle of chemical interactions involved in life is susceptible 

 of some experimental analysis into separate interactions which 

 may be studied by purely chemical methods ; secondly (at least 

 to the minds of many), with a steady faith that full acquaintance 

 with such separate interactions will ultimately be followed by 

 some knowledge of the manner in which they are co-ordinated 

 in the bioplasm. There are, indeed, chemical happenings in the 

 living cell itself which are to be looked upon as isolated from 

 the bioplasm, interactions which may be termed interplasmic 

 rather than intraplasmic. When an amoeba has ingested food 

 material, the digestive processes which go on, though intra- 

 cellular, are strictly interplasmic in the sense mentioned, as it 

 is to be supposed that suitable enzymes become operative 

 in the vacuole with which the food particle is quickly sur- 



