CARL LUDWIG. 171 



ing at physiological facts, remarks " that the heart is at 

 once the most delicate and strongest of all our organs, 

 because when excited by weak stimuli, it always responds 

 with a strong contraction — in fact, with its strongest possible 

 response" (Die Nation, 29th June, 1895). 



As regards the heart and the cause of its rhythm, quite 

 a number of the older theories regarding its rhythmical 

 action have been put aside, largely owing to the results 

 obtained by this method. It is, at least, something to get 

 rid of false theories. 



Keeping still to this method of perfusion, it has had a 

 far-reaching influence. The writer can well remember with 

 what diligence Luciani, now Professor of Physiology in 

 Rome, perfused blood through the excised heart of a frog, 

 and studied the remarkable groups of beats, with inter- 

 vening pauses, which bear his name of " Luciani's groups". 



In the opinion of the writer about this time there 

 commenced a movement of young men from Italy and 

 Leipzig which has exerted a great, not to say commanding, 

 influence on the physiological achievements of our Italian 

 confreres. 



Under the guidance of Kronecker, then the assistant 

 of Ludwig in the experimental department, Luciani studied 

 with patience the remarkable periodicity in the action of 

 the frog's heart whereby groups of beats alternate with 

 periods of repose. 



The artificial circulation of blood through excised organs 

 was obviously capable of great expansion. Ludwig pro- 

 posed to A. Mosso to study artificial circulation in an 

 excised kidney, and the writer remembers what lively 

 interest was awakened in the laboratory by the earliest 

 experiments, i.e., to study the life of a kidney after death. It 

 was soon discovered that even twenty-four hours after the 

 kidney was excised from the body, this organ still lived or 

 survived, or at least that its blood-vessels did, and responded 

 to the action of drugs. 



From these investigations originated the idea suggested 



by Ludwig to Mosso of measuring the volume of an organ 



due to variations in the size of its blood-vessels. Mosso 



12 



