622 



SCIENCE 



[N. S. Vol. XLIV. No. 1140 



If, now, we consider the advance of 

 physiological knowledge from the stand- 

 point of the efforts which have been made, 

 not to ascertain the causes of vital activ- 

 ity, but to track out its normal details, the 

 past history of physiology takes on a new 

 aspect. It becomes a record, not of dis- 

 heartening repulse before a hopeless wire 

 entanglement, but of continuous progress. 

 The new physiology of which I wish to 

 speak to-night is a physiology which delib- 

 erately and consciously pursues this line of 

 progress, leaving on one side what one may 

 call the ' ' causal ' ' physiology handed down 

 to us from the last generation. This new 

 physiology is in one sense not new, but 

 very old. It is only new in the sense of 

 consciously pursuing an aim which has 

 nearly always been instinctively pursued 

 by physiologists, and particularly by the 

 great physiologist from whom this society 

 takes its name. 



Now I think that many of my hearers 

 will at once say that such a course may be 

 useful up to a certain point, but that it is 

 not true science, and that therefore we can 

 not desert the old attempts. We must, in 

 fact, still continue our frontal attacks on 

 the wire entanglement. To this criticism I 

 shall endeavor to reply later. But mean- 

 while I should like to explain more clearly, 

 and by means of examples, what the new 

 physiology aims at. 



Perhaps I can do this most directly by 

 referring first to the corner of physiology 

 which has largely occupied my own atten- 

 tion — the physiology of breathing. 



When we count the breaths, or measure 

 their depth, we find much irregularity, as 

 if there were no very definite or exact regu- 

 lation of the breathing. Any active occu- 

 pation, such as speaking or singing, inter- 

 feres in various ways with the breathing, 

 and the impression at first produced is that 

 the regulation of breathing is very rough. 



It is also commonly believed that by spe- 

 cial training we can increase, or "im- 

 prove," the ventilation of the lungs. On 

 the other hand it has been well known for 

 long that the breathing is more or less 

 regulated to correspond with the consump- 

 tion of oxygen and production of carbon 

 dioxide in the body. Thus during heavy 

 muscular exertion greatly increased breath- 

 ing accompanies the greatly increased 

 oxidation in the tissues. Another fact, well 

 known to physiologists, is that if the lung 

 ventilation is by artificial or voluntary 

 means greatly increased for a short time, 

 there follows a period of "apnea," during 

 which natural breathing is absent. The 

 exact cause of this apnea was till recently 

 obscure. In 1868 Hering and Breuer 

 showed that the inflation of the lungs in 

 inspiration gives rise to impulses passing 

 up the vagus nerves, and inhibiting fur- 

 ther inspiratory impulses from the respira- 

 tory center, at the same time starting ex- 

 piration. Deflation of the lungs in expira- 

 tion has a converse effect. So long as the 

 vagi are intact they are constantly playing 

 this game of battledore and shuttlecock 

 with the respiratory center, and Hering 

 called this the "self-regulation" (Selbst 

 steuerung) of breathing. The apnea fol- 

 lowing excessive ventilation of the lungs 

 was interpreted by subsequent physiol- 

 ogists as the summed inhibitory effect of 

 repeated distentions. Fredericq showed, 

 however, that apnea is produced when the 

 respiratory center of one animal is supplied 

 with blood from another animal the lungs 

 of which are excessively ventilated. This, 

 therefore, is a true "chemical" apnea, due 

 to over-aeration of the arterial blood, and 

 was distinguished from "vagus" apnea. 

 Nevertheless the correlation of the various 

 "factors" apparently involved in the regu- 

 lation of breathing remained extremely 

 obscure. 



