LIFE AND WRITINGS OF ROBERT WHYTT, M.D. 117 



Flourens, Muller, W.P. Alison, Marshall Hall. Marshall Hall's conclusions, 

 though not all implicitly received, are undoubtedly, for the most part, in advance 

 of all previous views. Dr Carpenter, while he admits the reflex action of the 

 cranio-spinal axis, in the sense taught by Marshall Hall, insists on its connec- 

 tion, for the maintenance of many complex acts, with sensation as existing in 

 the sensory ganglia or nervous parts whence the nerves of special sense originate. 

 Under the name " ideo-motor," he describes such acts as those of the somnambulist 

 as being the result of a reflex action of the cerebrum itself, while he applies the 

 expression " unconscious cerebration," to a supposed reflex action of the cerebrum 

 which may proceed without the knowledge of the individual, so as to evolve in- 

 tellectual products in the shape of new views of subjects previously before the 

 mind. On this latter point, Dr Laycock entertains similar opinions, and appears 

 successfully to have vindicated to himself the claim of having been the first who 

 conceived the idea of a reflex action of the cerebrum. This idea is highly ingeni- 

 ous, and plainly an extension of that developed by Whytt, but it requires a 

 larger consideration than the limits of this memoir permit. 



The starting point in the further investigation of this subject is obviously the 

 following acknowledged fact, the close correspondence between which and Whytt's 

 view is indisputable — an impression made on the peripheral extremity of a nervous 

 thread is conveyed to a segment of the cranio-spinal axis, and is imparted to one 

 of the cells in its vesicular substance, whence an influence is transmitted horizon- 

 tally, by means of a white internuncial thread, to a cell of the like substance, where 

 motor power being generated is made to act on a contractile fibre, by a nervous 

 thread extended between the motor-cell and that fibre. 



This faculty of motion may be described as a primary power of the living frame ; 

 that is, as conferred upon it by its original constitution. It seems not improbable 

 that peripheral impressions are, by the same original constitution of the frame 

 adjusted to the production of even very complex motions, without any controlling 

 influence from other parts of the nervous centre. In one of Mayo's experiments, 

 when the sole of the foot was pricked, after division of the spinal cord in the 

 back, the foot was suddenly retracted "with the same gesture as it would have 

 been during life." The extent to which the skeleton muscles must be called into 

 activity in automatic acts, produced by peripheral impressions, long before volition 

 begins to be exercised, cannot but be very great. Hence, probably, the early 

 extensive exercise of this primary reflex action, in the infant, may have very 

 momentous effects on the development of the whole function of locomotion in the 

 living frame. 



Besides peripheral impressions, there is another extensive set of causes con- 

 tinually in force from the earliest infancy to the production of automatic acts in 

 the skeleton muscles; namely, emotions, passions, and the various instinctive 

 affections which originate in mental operations. This set of causes, doubtless. 



