374 PHYSIOLOGY CHAP. 



produced contraction of the internal anal sphincters, ischemia of 

 the rectal mucosa, slight pallor of the cervix and body of the 

 uterus on the opposite side, etc. Langley (assisted partly by 

 Anderson) obtained similar results for the pilomotor muscles and 

 the cutaneous blood-vessels in the thoracic and lumbar regions. 



But, according to Langley, none of these reactions, in which 

 excitation of the central end of a sympathetic trunk after 

 separation from the higher centres causes motor or secretory 

 effects, are true reflexes. His arguments and interpretation will 

 be better understood by giving a specific example : 



If the lateral strand of the sympathetic be cut in the cat 

 immediately above the 7th lumbar ganglion, and the central 

 (cranial) end stimulated, erection of the hairs with contraction of 

 the blood-vessels will be seen in the cutaneous regions innervated 

 by the 4th and 5th lumbar roots. The same effects may be 

 obtained many days after, when sufficient time has elapsed for the 

 degeneration of afferent nerve-fibres with trophic centres below the 

 level of section. It follows that the excitation in this case is not 

 conducted by fibres whose trophic centres lie in the lower portion 

 of the sympathetic. If the nerve - roots of the 4th or 5th 

 lumbar ganglion are now cut the reaction described disappears 

 after five days. We must, therefore, conclude that the excitation 

 was transmitted by pre-ganglionic efferent fibres. 



This striking fact that the supposed reflex ceases on degenera- 

 tion of the pre-ganglionic fibres is, according to Langley, common 

 to all so-called " sympathetic reflexes " hitherto described. 



The only possible explanation he can find is that each pre- 

 ganglionic fibre divides into several collaterals, and sends branches 

 to different ganglia. Stimulation of the central end of one of 

 these fibres causes an excitation that is at first propagated back- 

 wards along the cut fibre, and then to another twig, until it 

 reaches the ganglion which gives origin to the post-ganglionic 

 fibres that evoke the reaction. In other words, this is a similar 

 process to that described by Klihne in his experiments on the 

 conduction of motor nerve in both directions. Langley has 

 proposed to call this special phenomenon by the name of pseudo- 

 reflexes or pre-ganglionic axon reflexes. Fig. 198 is a diagram 

 of the course of the excitation as compared with a true reflex. 

 Langley utilised these pseudo- reflexes for the purpose of ex- 

 perimentally determining which pre-ganglionic fibres are connected 

 with different ganglia. 



He concludes : " In my opinion none of the ' apparent ' reflexes 

 of the autonomic ganglia depend on a reflex mechanism similar to 

 that which subserves reflexes in which the central nervous system 

 is concerned, as in no case is an afferent fibre concerned in the 

 process." l 



1 Langley, Ergebnisse der Physiologic, 1903, Jahrgang ii. Abteil. ii. p. 859. 



