i64 THOMPSON YATES LABORATORIES REPORT 
plantar flexion of the contra-lateral ankle. Similarly, in the Cat, when Ilird, IVth, Vth, Vlth, 
Vlllth, IXth, and Xth post-thoracic afferent roots have been severed after spinal transection at 
Xlth thoracic level, a pinch on sole or dorsum pedis, or lateral aspect of lower region of leg and 
calf, evokes idio-lateral flexion of toes, ankle, and knee, with some contraction in the idio-lateral 
gracilis, but contra-lateral plantar flexion of ankle. Again, the reflex that I call the torticollis 
reflex^ breaks this '2nd law' of Pfluger, because it employs muscles on both sides of the median 
plane, and the muscles on the crossed side are not symmetrical with those on the uncrossed. 
Pfluger's 3rd law* states that if a spinal reflex is bilateral, the movements on the side 
opposite to that stimulated are much weaker than the idio-lateral. This is the so-called law of 
unequal intensity of bilateral reflexes. The experiments in Cat, Dog, and Monkey aiFord 
instances of it. 
When, from one fore-paw, bilateral movement of the fore-limbs is excited, the movement is less 
forcible on the crossed side and also less ample. 
When excitation of one pinna evokes bilateral movement in the hind-limbs as described above, the 
crossed movement is the weaker. 
When bilateral retraction ot abdomen is excited from the chest wall the crossed retraction is much 
the less extreme. 
In the above described asymmetrical progression reflex the crossed movement is much the less 
vigorous. 
In the bilateral ' whisker reflex ' the crossed movement is the less ample. 
But some reflexes controvert the law. 
Both in the Monkey and in the Cat and Dog a touch on the side of the tail at its root 
usually evokes abduction from the median line and away from the side stimulated. This recalls 
Luchsinger's reflex from the tail of the Newt. The same crossed action is obtainable, as stated 
in the list of root-reflexes, p. 125, from the dorsal (afferent) roots of coccygeal nerves. Again, a 
pinch of little toe or a pin-prick at the inner edge of the ischial callosity in Monkey often elicits 
a similar switch of the tail from the idio-lateral side. This reflex not only breaks the 3rd law, 
but also 1st law, which lays down that if a movement caused by a spinal reflex is unilateral, it 
occurs always on the same side as the application of the stimulus. Caudal lateral movement of 
reflex spinal origin is, however, not always abduction from the side stimulated. 
Conduction across the median sagittal plane of the cord is certainly very unequally facile 
at different spinal levels. I have found it curiously difficult to drive irradiation across in the 
thoracic region from a thoracic afferent root, so as to elicit bilateral action of intercostal muscles. 
It is easier in Cat, Dog, and Monkey to obtain cross-reflex from one hind-limb to the other than 
from one fore-limb to the other. It is easier to obtain in these species cross reflex from one hind- 
limb to the other than from a hind-limb up to a fore-limb. It is, however, easier to obtain a 
reflex from fore-limb to idio-lateral hind-limb than from fore-limb to fore-limb. In the hind-limb 
of Cat and Dog, the extensor neurons of knee, hip, and ankle have more facile communication 
with the crossed side of the cord than have the flexor neurons, but this does not seem the case 
with the hind-limb of the Rabbit. 
* Loc. cit. 
