32 THE TONER LECTURES. 



Phys. Classe. 1870, Bd. xxii.) is the first experimenter to whose 

 original paper I have had access, who proved that after separa- 

 tion of the medulla frojn the pons irritation of a sensitive nerve 

 still causes a great increase of the arteiial pressure. Thus in 

 his experiment a (p. 33) on a rabbit, the medulla having been 

 previously cut, the pressure rose 29 millimetres in 16 seconds, 

 and in experiment 6, both peduncles of the crus cerebri having 

 been previously divided, the rise amounted to 30 millimetres. 



I. Owsjannikow (Berichte, etc.^ Bd. xxiii.) has experimented 

 very elaborately, and has found that in cats and rabbits the 

 vaso-motor centre is in a space whose upper boundary is one 

 or two millimetres below the corpora quadrigemina, and whose 

 lower boundary is four to five millimetres above the point of the 

 calamus scriptorius, a space of about four millimetres. 



Owsjannikow divided the nerve centres with very fine knives 

 and employed the effect upon the arterial pressure of gal vanizing 

 a sensitive nerve as a test of the integrity of the vaso-motor 

 centre. His experiments have every appearance of care and 

 accuracy. 



Pv. Heidenhain (PJluger^s Archiv, Bd. iv. p. 552, 18T1) has 

 also, in numerous experiments, determined that separation of 

 the medulla from the pons in dogs does not prevent the rise 

 of arterial pressure when a sensitive nerve is irritated. 



The results obtained severally by Dittmar, Owsjannikow, 

 Heidenhain, and myself are therefore in accord, and seem to 

 prove that the chief vaso-motor centre is in the medulla 

 oblongata, probably in the exact position indicated by Ows- 

 jannikow. 



It does not follow, however, that this centre in the medulla 

 is the sole generator of vaso-motor force. It is much more 

 probable that it is simply of the nature of a governing or start- 

 ing centre, and that the chief generators of vaso-motor force 

 are placed in the cord. These cells, if they exist, may, under 

 ordinary circumstances, not have the power of generating vaso- 



