852 SOCIÉTÉ DE BIOLOGIE 



As arterial pressure falls, the circulation rate is slower and the 

 oxygen supply to the tissues is less. Inadéquate oxygen supply results 

 in partial oxidalion, \\ilh deveiopment of lactic acid (Araki), and with 

 conséquent réduction of the alkali reserve. 



6. The lower the arterial pressure the lower the alkali reserve. 

 From the foregoing considérations this resuit is to be expected. 



7. Damage to the control of the circulation. — Nerve cells are spe- 

 cially sensitive to oxygen-lack. If hlood pressure continues below the 

 critical level, sensitive structures are injured. Vasoconstrictor tone 

 gradually diminishes (Erlanger). Finally transfusion or infusion 

 causes no permanent rise of pressure ; the effect is that seen after the 

 medulla is destroyed (Dijon experiments). 



8. Sensitiveness to ether. — The injured vasoconstrictor centre is 

 further depressed by the anfesthetics, ether and chloroform, and blood 

 pressure consequently drops to a lov^'er level. 



Tue Cause of Suock. 



1. It is not due primarily to loss of vasoconstrictor tone, for reasons 

 stated above. 



2. It is not due to fat embolism; for, a) too much fat is required to 

 check Ihe flow of blood through the lungs (2 ce. per kilo in dogs), 

 0) venous pressure in man is not raised as in expérimental fat embolism, 

 c) the peculiar hyperpnœa or apnœa, seen in expérimental fat embo- 

 lism, does not occur in man. 



3. It is not due lo " acapnia '". The excessive respiration demanded 

 by this Iheory is not seen in human cases. 



4. Evidence that it is due to the etîect of lissue injury (experiments 

 in coopération wilh Bayliss and at Dijon ; Cf. Delbet, Quénu) : 



a) The crushing of muscles iri a hind leg is followed by a fall of 

 arterial pressure beginning in about 20 minutes and reaching in about 

 an hour a shock level. -~ 



b) This effect occurs even though nerves to the leg are severed; it is 

 therefore not of nervous origin. 



c) If the blood vessels (iliac artery and vein) of the leg are tied and 

 the muscle injured, the pressure drops only after the blood tlow is 

 restored. 



d) If a shock pressure has been caused by muscle injury, lying the 

 vessels may be followed by a progressive rise of pressure to the normal 

 level. 



e) The effects of muscle injury may pass away with spontaneous 

 recovery of pressure. 



f) The lowered pressure after injury is not primarily due to extra- 



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