I. — PHYSIOLOGY. 153 



possible by the breathing of some neutral gas, such as nitrogen, and you 

 will find that only with difficulty will you endure half a minute. Yet 

 even such a test gives no real picture of the impotence of the machine 

 — which is the brain — to ' caiTy on ' in the absence of oxygen. For, 

 on the one hand, nearly a quarter of a minute elapses before the reduced 

 blood gets to the capillary in the brain, so that the machine has only 

 carried on for the remaining quarter of a minute; on the other hand, 

 the arterial blood under such circumstances is far from being com- 

 pletely reduced — in fact, it has very much the composition of ordinary 

 venous blood, which means that it contains about half its usual quotum 

 of oxygen. It seems doubtful whether complete absence of oxygen 

 would not bring the brain to an instaiitaneous standstill. So convincing 

 are the experimental facts to anyone who has tested them for himself 

 that I will not further labour the power of anoxaemia to stop the 

 machine. I will, however, say a word about the assumption which I 

 have made that the machine in this connection is the brain. 



It cannot be stated too clearly that anoxaemia in the last resort must 

 affect every organ of the body directly. Stoppage of the oxygen supply 

 is known, for instance, to bring the perfused heart to a standstill, to 

 cause a cessation of the flow of urine, to produce muscular fatigue, and 

 at last immobility, but from our present standpoint these eSects of 

 anoxaemia seem to me to be out of the picture, because the brain is so 

 much the most sensitive to oxygen want. Therefore, if the problem is 

 the stoppage of the machine due to an insufficient general supply of 

 oxygen, I have little doubt that the machine stops because the brain 

 stops, and here at once I am faced with the question how far is this 

 assumption and how far is it proven fact ? I freely answer that research 

 in this field is urgent ; at present there is too great an element of assimap- 

 tion, but there is also a certain amount of fact. 



To what extent does acute anoxasmia in a healthy subject wreck the 

 machinery as well as stop the machine? By acute anoxaemia I mean 

 complete or almost complete deprivation of oxygen which, in the 

 matter of time, is too short to prove fatal. It is not easy to obtain 

 quite clear-cut experiments in answer to the above question. No 

 doubt many data might be quoted of men who have recovered from 

 drowning, &c. Such data are complicated by the fact that anoxaemia 

 has only been a factor in their condition; other factors, such as 

 accumulation of carbonic acid, may lalso have contributed to it. 

 The remarkable fact about most of them, however, is the slight- 

 ness of the injury which the machine has suffered. These data, 

 therefore, have a value in so far as they show that a very great degree 

 of anoxaemia, if acute and of short duration, may be experienced with 

 but little wreckage to the machine. They have but little value in show- 

 ing that such wreckage is due to the anoxaemia, because the anoxaemia 

 has not been the sole disturbance. Of such cases I will quote two. 



The first is that of a pupil of my own who received a gunshot 

 wound in the head, to the prejudice of his cerebral circulation. I 

 can give you the most perfect assurance that neither intellectually 

 nor physically has the catastrophe which befell him caused any 

 permanent injury. For the notes of the case I am indebted to 



