CONCLUSIONS AS TO THE RESPIRATORY MECHANISM. 463 



arterialized condition than usual, which stirs up the respiratory 

 center to increased activity. On examination, however, it is 

 found that the blood leaving the left side of the heart in such 

 cases is not the less arterialized, but, if anything, more arte- 

 rialized than usual." . . . "Obviously the blood coming 

 from the tetanized muscles affects the respiratory center by 

 virtue of some quality which, unlike that due to the deficiency 

 of oxygen or excess of carbonic acid, is not immediately affected 

 by the passage through the lungs. Whether the quality in 

 question be dependent on an excess of sarcolactic acid, or on 

 some other product or products of muscular metabolism, we 

 do not as yet know." It is very clear, from all this, that it 

 is not the venous blood that reaches the medullary centers 

 which gives rise to the phenomena witnessed, but the products 

 of metabolism themselves, which react upon the anterior pitui- 

 tary body, and through it upon the adrenals, as do other poisons. 

 Indeed, if we consider the course of events in cases of 

 asphyxia, the "general convulsions of the whole body, which, 

 however, have to a certain extent an expiratory character," fol- 

 lowed by "exhaustion," which "begins to set in," the rhythm 

 becoming "slower than proportionate to the weakening of the 

 individual movements," the part played by the suprarenal sys- 

 tem affirms itself, combined with and aggravated by the gradual 

 decline of all physiological processes that depend upon proper 

 aeration of the blood. Again, therefore, does the "respiratory 

 center" in the medulla show itself unable to stand analysis. 

 Asphyxia, moreover, is not due, evidently, to the action of 

 C0 2 upon a medullary center; its active symptoms are due to 

 intoxication by products of metabolism, while its passive phe- 

 nomena air-hunger, cyanosis, etc. are the result of gradually 

 declining functional activity. On the whole, the following con- 

 clusions seem warranted: 



1. There is no individual center in the medulla oblongata to 

 which the term "respiratory center" can be applied. 



2. The morbid phenomena witnessed after section of the me- 

 dulla are due to interruption of the stream of general motor im- 

 pulses which the medulla serves to transmit. 



3. There is no individual center in the medulla oblongata to 

 which the term "vasomotor center" can be applied. 



