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Croonian Lectuee : The Respiratory Process in Muscle 

 and the Nature of Muscular Motion. 

 By Dr. W. M. Fletcher, F.R.S, and Prof. F. G. Hopkins, F.E.S. 



(Lecture delivered December 9, 1915.— MS. received November 22, 1916.) 



Me. President and Fellows: — We are keenly sensible of the honour 

 done to us in our being called to lecture on this occasion, and in making 

 this acknowledgment we would express our special gratification in being 

 so enabled to pay this act of piety to the memory of William Croone, 

 whom we commemorate to-day. The Croonian Lecture was founded through 

 his generosity in order to encourage the study of muscular motion, but some 

 sixteen years have now passed since that subject was last treated by the 

 Lecturer. During those years many additions have been made to our 

 knowledge of the subject, and great changes have resulted in our views of 

 it. It is a pleasure to us that we have now the opportunity of taking up 

 again the broken thread of the series, and of turning to-day to the chosen 

 subject of Croone's own enquiries and chief interest. We could wish that 

 a time more free from other occupations and anxieties than the present had 

 allowed us to do this less unworthily. 



Croone found in muscle the chief immediate hope of studying the energy 

 discharges of living elements, and it was surely an enlightened instinct 

 which led him to foresee, however dimly then, what we must recognise as 

 still true after this lapse of two and a half centuries. We still must look to 

 the study of muscular motion as the most fruitful, and perhaps for some 

 time to come the only, avenue to intimate knowledge of the modes of 

 eneigy discharge by the living cell, and of their relation to the specific 

 chemical processes of life. More than this, it is the study of muscle activity 

 which has so far given us all we know of the meaning of respiration as the 

 accompaniment of life. The study of respiratory exchanges in, the lungs 

 and in the blood of mammals has given us valuable lessons, and has 

 unfolded attractive stories of animal adaptation to environment. » That 

 study takes its place in the natural history of the Vertebrates, and has a 

 living value for the purposes of human medicine. It is describing to us 

 the modes in which oxygen reaches and carbon dioxide leaves the cell 

 under the anatomical conditions of the vertebrate animal, but it does not 

 attack the intimate problems of respiration as a process of animal cell life 

 in general. Croone, of Cambridge, was too close in time and sympathy to 

 the genius [of Mayow, and to the work of his other contemporaries at 



