414 PHYSIOLOGY CHAP. 



depressed from any cause. The number of steps in each locomotor 

 period bears no proportion to the successive pauses, as we noted 

 in the analogous phenomena of periodic cardiac and respiratory 

 rhythm (Vol. I. Chaps. IX. and XIII.). These and other facts for 

 which we have no space are evidence in favour of the fundament- 

 ally automatic nature of the activity of the locomotor centre. 



Fano tried to localise the centre for progression in tortoises by 

 Owsjanuikow's method of successive sections of the bulb. He 

 found it was limited to its lower third, and that it thus coincides 

 with the localisation of the centre for general reflexes in the 



FIG. 218. Curve of progression of clecerebrated tortoise, which had a brush dipped in anilin solution 

 fastened to its tail. (Fano.) The curve is reduced to T n . The arrows show the direction of 

 tin- movement ; the small breaks, the points at which the animal stopped. 



rabbit. To us, however, it seems more probable that the lower 

 third of the bulb is related to the true locomotor centre as the 

 nceud vital of Flourens is to the true respiratory centre this, as 

 we have seen, being far more extensive, and probably including 

 the whole region of the formatio reticularis. 



The bulb is necessary not only for walking but also for active 

 posture, that is, the capacity for remaining in a given posture or 

 attitude, and resuming it when passively disturbed. In order to 

 take up or maintain its natural pose, the animal must throw a 

 number of muscles into activity. The tendency to take up a 

 normal attitude seems more marked in the lower than in the 

 higher vertebrates. 



We know from the experiments of Renzi, Vulpian, and more 



