350 The Philosophical Society of Glasgow. 



columns, so as to furnish delicate sheaths or inclosures for these cells, 

 through which the radiating processes run into the neighbouring parts 



Dr. Thomson gave a general account of the facts which the speci- 

 mens exhibited as to the course of fibres in the cord ; but he confessed 

 that the knowledge of this subject must still be considered as extremely 

 imperfect. In fact, there are no more complicated problems in ana- 

 tomy than those relating to the course of fibres in the nervous centres ; 

 and a vast number of observations, made in different modes, will be 

 required to render the results of inquiry satisfactory in this part of the 

 subject. 



His observations, and those of Dr. Reid, confirmed the fact of the 

 fibres of the anterior roots running in numbers, and very directly, 

 towards the multipolar cells of the anterior horns of gray matter ; the 

 passage of a certain number of the fibres of the anterior roots through 

 the anterior commissure to the opposite side; and the junction of a part 

 of these fibres both with the anterior and lateral fibrous columns of the 

 cord on the same side. 



The structure of the anterior and posterior, and also of the lateral 

 vesicular columns, was very clearly demonstrated, and specimens were 

 shown, illustrating the peculiar nature of the posterior cornua of the 

 gray substance. 



Into these last the fibres of the posterior roots were seen to enter, 

 to bend round, and subsequently to pass in three directions — \st, for- 

 wards towards the vesicular columns and anterior roots ; 2d, into the 

 posterior vesicular, and into the posterior and lateral fibrous columns ; 

 and, Zd, in considerable numbers to cross or decussate both in the ante- 

 rior and posterior parts of the commissure. At the same time, Dr. 

 Thomson stated that he did not consider our present knowledge of the 

 connection or course of these fibres as sufficient for physiological or 

 pathological application. In particular, the difference between the 

 reflex motory and sensory fibres has not yet been shown, nor has the 

 physiological difference between the crossing of the effects of lateral 

 injury of the cord on the sensory and motory functions received its ana- 

 tomical explanation from the examination of the structure of the cord. 



Dr. Thomson expressed his belief, however, that at no very distant 

 period, from the number and ability of the inquu-ers at present engaged 

 in researches on this subject, we may hope to see important light 

 thrown upon many parts of it. He stated his belief in the existence 

 of frequent communications between certain fibres of the sensory 

 and motory roots in the spinal marrow (and that probably by means 

 of nerve-cells), as the means by which reflex motions are excited ; 

 and he adverted to the explanation which might thus be given of the 



