vni THE HIND-BEAIN 439 



equilibrium ; after a time it i'alls less frequently. This gradual 

 restitution of function is only to a small extent due to organic 

 compensation, and depends far more upon functional compensation, 

 on the gradual acquisition of new acts and movements, which are 

 capable of compensating the effects of cerebellar deficiency, and of 

 preventing loss of equilibrium and the tendency to fall towards 

 the injured side. By the curving of the vertebral column the 

 weight of the hind part of the body is thrown towards the affected 

 side, and thus falls chiefly on the opposite hind-limb, i.e. the hind- 

 limb unaffected by the operation. By abduction of the fore-limb 

 it widens the basis on which the body rests, lowers its centre of 

 gravity, and makes the passive flexion of the fore-limbs in the 

 various joints more difficult. 



Eeproduction of the footprints gives a record of these com- 

 pensating processes and a more minute analysis of the gait. The 

 normal tracing of the dog's ordinary walk is not always perfectly 

 equal and regular, but varies not only with the age and size of 

 the individual, but also with its race, as shown in the examples 

 of Fig. 232. To understand this tracing it must be remembered 

 that the ordinary step of the dog is made by alternate setting 

 down and lifting up the two diagonal pairs of feet, and that both 

 the setting down and the lifting up of the fore-limbs precedes 

 those of the hind-limbs, so that four distinct taps occur at regular 

 intervals, as can be proved by listening when the animal walks 

 upon a wooden floor. 



If we examine the tracing of the footsteps of a bitch in which 

 the right half of the cerebellum had been completely extirpated, 

 it is seen to be very different from the normal (Fig. 233). Tracing 

 b was taken two months after the operation ; the animal held the 

 principal axis of its body* curved to the right and oblique to the 

 direction of progress, so that the limbs of the right side were 

 more raised and abducted than in the normal, and the left limbs 

 adducted. It shows this alteration in the gait very plainly, 

 especially in the marked displacement to the right of the foot- 

 prints of the hind-limbs, the varying length and force of the step, 

 and the irregularity of the two lines which join the prints of the 

 fore-paws, which normally are almost parallel. A year after the 

 operation tracing c was taken from the same bitch, and showed 

 greater regularity of gait, although the displacement to the right 

 of the footprints of the hind-limbs still persisted, though it is less 

 pronounced. After blindfolding the animal's eyes tracing d was 

 taken, and shows that the gait was not much altered from that 

 with the eyes open ; but the direction of progress was uncertain, 

 the steps shorter, and the fore-limb more abducted. Tracing e 

 was taken a few minutes after the subcutaneous injection of 

 30 cgrms. of morphine hydrochlor. and shows exaggeration of all 

 the above anomalies in the animal's gait. 



