88 SCIENCE PROGRESS 



advance of recent years has occurred in connection with 

 respiration and the respiratory functions of the blood. The 

 reactions of haemoglobin with oxygen in the presence of salts, 

 acids, and carbon-dioxide have exhibited the most striking 

 adaptation to the needs of the animal under a wide variety of 

 conditions ; in fact, seeing that a chemical compound is a fixed 

 and not an adaptable thing, one might almost say that the 

 evolution of the animal in its present form has hinged upon 

 the physical properties of haemoglobin, as that of the plant has 

 depended upon those of chlorophyll. The physical properties 

 and reactions of these two pigments are still only imperfectly 

 understood, and progress in the studies associated with either 

 depends to-day more on progress in knowledge of the physico- 

 chemical basis of their reactions than on any biological factor. 

 The haemoglobin and the chlorophyll reactions are good examples 

 of the way in which physiology is dependent on physics and 

 chemistry for all possibility of further advance. The COg- 

 carrying power of the blood, and the exact regulation of the 

 respiration and of the hydrogen-ion concentration of the blood 

 by the respiratory centre and kidneys, are also examples of the 

 way in which exact methods are exposing the exquisite co- 

 ordination of the body, a co-ordination physical in its precision 

 and mechanism, biological in its complete adaptation to the 

 needs of the animal. 



The growth of biochemistry in the last twenty years has 

 opened up a field of work whose limits are seen to widen yearly, 

 both from the point of view of fundamental knowledge and 

 more especially from that of practical importance. The 

 achievements of biochemistry however, great as they have 

 been, have only served to emphasise our extreme ignorance of 

 the actual mechanism by which the chemical activities of the 

 animal are conducted, and to show the vast importance of the 

 things still remaining to be done. The synthesis, by chemical 

 means, of the organic compounds occurring as a result of the 

 activity of the living cell, and the discovery of the chemical 

 nature of other such substances not yet synthesised, have 

 proceeded side by side with the realisation of the importance 

 to the animal of various chemical bodies — the vitamines — 

 still unidentified. The " chemical correlation " also of the 

 functions of the body, though undoubtedly an essential part 

 of the animal's economy, depends mainly upon chemical 

 substances still unknown, and upon reactions with them of 

 unknown elements in the cells of the various organs. Pharma- 

 cology, the science of the action of drugs upon the normal and 

 the abnormal tissues, remains an empirical science, no clue 

 practically being available as to the mode of working of the 

 active drug, nor as to why small changes in its chemical or 



