and Nervous Filaments into Motive and Sensitive, 71 



by double roots ; one set of filaments emerging from the anterior, an* 

 other from the posterior, portion of the chord. It was in general noticed, 

 too (as by Coiter, and C. Bauhinus, 1590), that these filaments, on issu- 

 ing from the chord, passed into a knot or ganglion ; but, strange to say, 

 it was reserved for the second Monro (1783), to record the special obser- 

 vation, that this ganglion is limited to the fibres of the posterior root 

 alone. 



Such was the state of anatomical knowledge touching this point, at the 

 close of the sixteenth century ; and it may now seem marvellous, that, 

 aware of the independence of the motory and sensitive functions, — aware 

 that of these functions the cerebral nerves were, in general, limited to one, 

 while the spinal nerves were competent to both, — aware that the spinal 

 nerves, the nerves of double function, emerged by double roots and termi- 

 nated in a twofold distribution, — and, finally, aware that each nervous fila- 

 ment ran distinct from its peripheral extremity through the spinal chord to 

 its central origin ; — aware, I say, of all these correlative facts, it may now 

 seem marvellous that anatomists should have stopped short, should not 

 have attempted to lay fact and fact together, shouldnothave surmisedthat 

 in the spinal nerves diiFerence of root is correspondent with difierence of 

 function, should not have instituted experiments, and anticipated by two 

 centuries the most remarkable physiological discovery of the present day. 

 But our wonder will be enhanced, in finding the most illustrious of the 

 more modern schools of medicine teaching the same doctrine in greater 

 detail, and yet never proposing to itself the question — May not the double 

 roots correspond with the double function of the spinal nerves ? But so has 

 it been with all the most momentous discoveries. When Harvey pro- 

 claimed the circulation of the blood, he only proclaimed a doctrine ne- 

 cessitated by the discovery of the venous valves ; and the Newtonian 

 theory of the heavens was but a final generalization prepared by fore- 

 gone observations, and even already partially enounced. 



The school I refer to is that of Leyden — the school of Boerhaave and his 

 disciples. — Boerhaave held with Willis that the brain-proper is the organ 

 of animality ; a distinct part thereof being destined to each of its two 

 functions, sense and voluntary motion ; — that the After-brain is the organ 

 of vitality, or the involuntary motions ; — and that the two encephalic or- 

 gans are prolonged, the former into the anterior, the latter into the posterior, 

 columns of the spinal chord. In his doctrine, all nerves are composite, be- 

 ing made up of fibrils of a tenuity, not only beyond our means of obser- 

 vation, but almost beyond our capacity of imagination. .Some nerves are 

 homogeneous, their constituent filaments being either for a certain kind 

 of motion alone, or for a certain kind of sensation alone ; others are he- 

 terogeneous, their constituent fibrils being some for motion, some for 

 sensation ; — and of this latter class are the nerves which issue from the 

 spine. On Boerhaave's doctrine, however, the spinal nerves, in so far as 

 they arise from the anterior column, are nerves both of sensation and 

 voluntary motion — of animality ; in so far as they arise from the posterior 



