38 THOMPSON YATES LABORATORIES REPORT 
move the limb in any which is an unnatural direction. But from the above given criteria 
co-ordination is abundantly shown to result from the independent power of the spinal arcs, 
altogether apart from the influence of the great cranial sense-organs and of the cerebral arcs 
superposed upon them. These senses and tlie brain find elementary co-ordination of the skeletal 
musculature an achievement already provided and to hand in the spinal cord itself. No doubt 
the product of the instrument is, with the instrument itself, given over to their use in the 
reactions they elicit from the spinal musculature. 
Now a co-ordinate movement must be 'purposive' in character. Considered in the light 
of the Darwinian theory, the normal connections between any afferent path {e.g. piece of skin) and 
the motor apparatus conjoined with it, can only be such as to lead to ' purposive ' movement. 
The question rises, what are the purposes of wliich the reflex movements of a spinal animal are 
indicative. 
It is curious that the sense-organs of both skin and muscle seem to evoke reflexly very much 
the same movements the one as the other. Irritation of the skin of the foot evokes flexion at 
knee and In'p ; so also doe,-, stretching the muscular sense apparatus in the muscles and ligaments 
at the pedal and atikle-joints. Certain reflexes are, however, peculiar to skin stimuli ; such are 
the 'scratch' reflex and the 'shake' reflex in the spinal dog. The former is started by stimuli 
applied to the skin of the trunk, perhaps especially of side, flank, and shoulder. It consists in a 
rhythmic flexion of the hind limb, causing it to execute scratching movement. The latter is 
started from the skin of the trunk, especially perhaps along the mid-dorsal line, and consists in a 
shake of the whole body, like that given by a dog on coming wet from water. I have seen it 
occur synchronously in the neck and head above the lesion, and in the 'spinal' part of the animal. 
Spinal transection had been performed at the sixth cervical level ; on scratching the skin over the 
scapula — partly anaesthetic, partly still sensitive- 'a shake' was induced in the musculature above 
as well as behind the lesion. Grainger* concluded years ago (1837) that spinal cutaneous reflex 
movements 'are either of a preservative character or resembling the motions which the function 
of the organ requires.' From the tegument of the spinal creature reflex movements of 'preening' 
or 'cleansing' can be elicited. The 'preening' actions of the spinal insect and crustacean fall 
into this category. The spinal frog wipes irritants from its skin. The posturing of the hind 
limbs and tail of the spinal dog concurrently with reflex evacuation of the faeces, keeping the body 
from being soiled, come into the same class of purpose as the 'shaking' and 'scratching' reflexes 
above mentioned. The conjunctival reflex closure of the eye, essentially a cutaneous, and, from 
the broad point of view, a spinal reflex, is similarly preservative of the sensorial surface whence it 
is initiated. 
Another purpose whicli seems unmistakably signified by spinal reflex movements is pro- 
gression. To apply the appropriate stim.ulus for this is perhaps a little difficult. Dytiscus, the 
water-beetle, when reduced to a spinal condition, does not run when placed on a firm surface, 
although each of its legs responds by free movement when individually stimulated. But on being 
* ' Functions of the Spinal Cord,' London. 
