PARALYSES IN DOGS 107 
Unfortunately, the ribs themselves were not counted, so that 
the possibility of variation must not be lost sight of, as a source 
of error. 
The most pertinent information is that obtained in the individ- 
ual case by comparing rights and lefts. Other things being equal, 
one may in certain cases, ascribe a unilateral effect toa correspond- 
ing unilateral lesion. In the same way by proper elimination, 
bilateral effects may sometimes be ascribed to bilateral lesions. 
It will be apparent that the collation of all the evidence according 
to numerical segments offers less exact conclusions than those 
which can be derived in the same individual and more especially 
with reference to the relative position of centers. But by com- 
paring relationships and detecting correspondence, certain infer- 
ences of significance may be obtained. Aside from the assump- 
tion that the upper leg centers are, generally speaking, higher 
than those of the lower leg, no further assumptions were used, 
except, of course, such as are based on the classical conceptions 
of the functions of anterior and posterior roots and of the white 
and grey matter of the spinal cord. 
Inferences from individual experiments: summary 
Experiment 64. (Figs. 6 and 7.) External popliteal paralysis on 
left not accounted for by slight anterior root damage as there was simi- 
lar damage on right where there was no paralysis. Therefore the exter- 
nal popliteal centers must be in the upper 7th lumbar segment, and by 
comparing right and left anterior horns, they must be in the dorsal two- 
thirds of the horn. Loss of left knee jerk accounted for by involve- 
ment of 5th and 6th posterior roots. If internal popliteal centers are 
at the level of or below the external popliteal centers (see Experiments 78 
and 86), paths for voluntary control seem to run in the anterior column. 
Experiment 78. (Figs. 8 and 9.) Weakness of right knee and hip 
best explained by involvement in 5th lumbar segment and anterior 
root filaments attached. As lesion in grey matter of middle 6th lumbar 
leg is bilateral and left leg seemed good, it could not account for paraly- 
sis of right external popliteal, which is consequently traceable to damage 
of right anterior roots attached to lower 6th and upper 7th lumbar seg- 
ments. Both internal popliteals being good, their centers must be lower 
than external popliteal centers, for they could not be higher on account 
of bilateral lesion just above, which les.on also suggests a possible gap 
between upper and lower leg centers. Extinction of right knee jerk 
explained by 5th and 6th anterior root involvement. Voluntary dor- 
