548 THE PATHOLOGY OF NIGIIT-SWEATIXG IN PHTHISIS. 



vated and the respiratory movements kept up, and the vaso- 

 motor centre, from which stimuli constantly proceeding to the 

 vessels keep them in a state of chronic contraction. 



Both these centres were formerly supposed to be situated in 

 the medulla oblongata alone, because when the medulla was 

 separated from the cord by a transverse cut at the level of the 

 occiput, respiration ceased, and the tonic contraction of the 

 vessels in the body at once ceased, and they became dilated. 



It was first shown by Schiff, however, that if part of the 

 medulla were destroyed, so as to cause the respiratory move- 

 ments completely to cease, the death of the animal, which w^ould 

 usually occur under such conditions, might be prevented by the 

 continuous use of artificial respiration for many hours. By 

 this process time was allowed for the remaining portion of the 

 medulla to learn, as it w^ere, how to perform the function of 

 the part which had been destroyed, as well as its own, so that 

 after artificial respiration had gone on for several hours, the 

 animal began to make feeble attempts to breathe, and these 

 became stronger and stronger, until at last respiration was again 

 established. It was thus shown that when a part of the respira- 

 tory centre in the medulla was destroyed, the remainder might 

 become sufficiently powerful to perform the functions of the 

 whole ; but the experiments of Prokop Eokitanski* have shown 

 that, instead of being limited to the medulla oblongata, as was 

 formerly supposed, the respiratory centre actually extends for 

 some distance down the spinal cord. When the medulla is 

 completely separated from the cord by a transverse cut of the 

 level of the occiput, respiratory movements usually cease, and 

 do not recommence. But if strychnia be injected into the 

 circulation immediately after the cord has been divided, the 

 respiratory movements again commence. It is evident that 

 these movements in this case do not depend upon the action of 

 the medulla at all, as they did in the experiments of Schiff', for 

 here the whole of the medulla has been cut off from any connec- 

 tion with the respiratory muscles, and the respiratory movements 

 must therefore depend upon stimuli proceeding to the respira- 

 tory muscles, not from the medulla oblongata, but from the- 



Vide antea, p. 323. 



