THE SYMPATHETIC SYSTEM OF NERVES. 547 



occur in both fibres, similar to those that have been so often 

 described as exhibited by non-medullated nerve fibres. After 

 running in company for a variable distance, the two fibres 

 separate from one another, and pursue an opposite course. 

 Both are essentially nervous, as is clearly shown by the cir- 

 cumstance that Arnold and Beale have been able to trace the 

 continuity of both processes with dark-edged motor fibres. 



The relation of the spiral to the straight fibre is subject to 

 great variation, both in reference to its thickness and to the 

 number of its coils. As a rule, the straight is thicker than the 

 spiral fibre, though the difference is sometimes not very well 

 marked, and is occasionally the reverse. The spiral fibre is 

 frequently multiple, and is then usually of smaller size than 

 when solitary. The number of coils is likewise very variable, 

 and in some instances the spiral character or type is not 

 apparent, the two fibres then running parallel to one another, 

 whilst in other cases the spiral fibre is wound round the straight 

 like a corkscrew. According to Beale, it is in young cells that 

 the spiral fibre is defective, whilst, on the contrary,, the older 

 the cell, the greater the number of the coils. In my investiga- 

 tions undertaken with this particular point in view, I have 

 convinced myself that the spiral fibre, though undoubtedly 

 very common, is not uniformly present in the sympathetic cells 

 of the Frog. Great differences exist in this respect in different 

 individuals, rendering it very probable that they stand in 

 relation with the various stages of development through which 

 the nerve cells pass. 



Arnstein and Kollmann, Courvoisier, Guye, and Bidder, all 

 essentially adopt the views of Arnold and Beale in regarding 

 both of the processes springing from the sympathetic cells as 

 nervous structures. Schwalbe is inclined to admit two kinds 

 of spiral fibres, one of a nervous nature, originating in the sub- 

 stance of the ganglion cell, and making only a few or no turns 

 around the straight fibre ; the other, which may be regarded as 

 produced by a thickening of the sheath, and as being developed 

 from a fibrous plexus at the base of the cell. Krause held the 

 spiral fibres as unessential structures, which were not of a 

 nervous nature, and believed that they either consisted of 

 an elastic fibre, or were referable to the foldings of the 



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