THE SPINAL ANIMAL 39 
plac«d in water it immediately swims * co-ordinately forwards. I find the spinal frog when placed 
in water at 38° C. swims for a short time co-ordinately forward with good bilateral strokes. Water 
at that temperature acts as a stimulus to the skin of the frog. The fish and triton after removal 
of the brain exhibit co-ordinate progression. In the dog, after spinal transection at the seventh 
cervical level, skin stimuli to the under surface of the body cause co-ordinate movements of all 
four limbs, the posture assumed taking the diagonal symmetry indicative of quadrupedal progres- 
sion.t Even when the spinal transection is in the lumbar region, pressure upon the pad usually 
elicits protraction and flexion of hip and knee in the homonymous hind-limb, and retraction with 
extension of hip and knee in the crossed hind-limb. The spinal reflexes significant of progression 
seem to contribute chiefly toward preparatory posture in readiness for onset of action executed by 
the musculature under the driving of higher centres. Thus the well-known reflex spinal posture 
of the frog is flexion of the hind-limbs, the extensors of the joints being taut and ready for the 
jump. Again with the primary reflex from the pedal end of the limb of the mammal. This 
does not, as might have been expected, take the form of the propelling stroke, the extensor push, 
that thrusts the body forward. On the contrary, it lifts the limb from the ground. This is, no 
doubt, the phase of the limb's movement of progression which requires the least output of force ; 
it resembles in so far the expiratory phase preparatory for the inspiratory of respiratory movement ; 
it may almost be likened to the diastole of the heart, and, like both these, it is preparatory for a 
succeeding phase of greater muscular effort. That phase ensues also in the spinal animal, but it 
is the less easy to obtain, and less soon emerges from the depression of traumatic shock. 
The spinal reflexes which in their results approximate most closely to the normal reactions 
of the unmutilated individual, are those connected with the pelvic and abdominal viscera. Defas- 
cation, micturition, parturition, menstruation, genital turgor, seminal emission — these and other 
analogous functions are executed as spinal reflexes in a manner presenting little or no physiological 
defect from the normal. Their ' purpose ' is clear. If the bulb be included with the spinal 
cord, and these together, including their peripheral nerves, be isolated from the rest of the nervous 
system, the animal as regards its visceral life, including that of the heart and lungs, is practically 
intact. The viscus concerned with the intaking of gaseous food is innervated from a cranial 
nerve, the vagus ; hence its ' nervous centres ' lie in the bulb. An important part of the 
circulatory muscles, namely the cardiac, is similarly innervated by a cranial nerve, hence likewise 
has a bulbar nervous centre. The existence of respiratory centres for the muscles of inspiration 
and expiration as independent from the bulbar centre remains still unproven. The existence of 
spinal vaso-motor centres subsidiary to the bulbar is asserted on the ground that it is still possible 
to obtain reflex alterations of blood pressure when the cord has been transected at calamus 
scriptorius if strychnia be exhibited to heighten its reflex activity. To demonstrate the existence 
of potent vaso-motor centres in the spinal cord does not, however, require the exhibition of strychnia. 
It is enough to allow the lapse of a few days or, better, weeks after transection of the cord in the 
cervical region. The blood pressure will then be found to have in the carotid of the dog a mean 
* Carpenter, ' Comparative Physiology,' London, 1850. 
f Sherrington, ' Joiirn. of Physiol.,' xx, 1897. 
