PHYSIOLOGY. 



583 



stimulated, and will produce a preganglionic 

 axon reflex. The author thinks that these results 

 support the view he had previously put forward 

 that no reflexes save axon reflexes occur from the 

 ganglion of the sympathetic system. 



In a study by the same author of the regenera- 

 tion of the preganglionic fibers of the sympathetic 

 system, the superior cervical ganglion in a cat was 

 excised, leaving a gap in the nervous tissue of 

 less than a centimetre. The cervical sympathetic 

 nerve did not recover its function for a year and 

 eleven months. The result was regarded as estab- 

 lishing a possibility that the preganglionic fibers 

 are unable to form direct functional connections 

 with the peripheral tissues. Direct stimulation 

 of the sclerotic, on the side on which the gan- 

 glion had been excised, did not give local dilata- 

 tion of the pupil. This had already been observed. 

 The fact affords evidence that all the fibers for 

 the radical contractile substance (dilator muscle) 

 of the pupil pass through the superior cervical 

 ganglion and have no nerve cells on their course 

 beyond this ganglion. Although the cervical 

 sympathetic did not recover its function, the nerve 

 strands beyond the place of section contained 

 numerous normal nerve fibers. After section of 

 the lumbar sympathetic trunk, no return of func- 

 tion was found for thirty days, a very slight re- 

 turn was found in thirty-five days, and a con- 

 siderable though not complete return in forty- 

 eight days. Broadly speaking, the pilomotor fibers 

 in regenerating establish functional connection, 

 first with the nearest ganglion, then with the next, 

 and so on downward. The new connections of the 

 various classes of nerve fibers in the several spinal 

 nerves are not made indiscriminately with the 

 several ganglia and with the different classes of 

 nerve cells in them. A marked tendency is ob- 

 served for the normal complex relations to be re- 

 established. But some abnormal connections are 

 made. On the view that nerve fibers grow out 

 from their nerve cells, it appears probable that 

 one factor in bringing about a re-establishment 

 of normal connection is a tendency of the several 

 cut fibers to grow to a certain definite length in 

 other words, that the axon process of each nerve 

 cell, whenever it is cut, will in favorable condi- 

 tions grow to its original length, neither more nor 

 less. 



It was observed by Von Monakov that after 

 hemisection of the spinal cord just below the pyra- 

 mids, the nucleus of Deiters underwent complete 

 ^ atrophy on the same side as the lesion. This au- 



branches to more than one ganglion. In the lower thor concluded, from an experiment on a single 



thoracic, the lumbar, and the sacral regions of the 

 sympathetic in the cat the great majority of the 

 fibers send branches to three ganglia ; a few send 

 branches to four. In the corresponding regions 

 of the dog the single nerve fibers appear commonly 

 to send to four ganglia, and probably to more. 

 In the upper cervical region many of the pre- 

 ganglionic fibers run to five or six ganglia in addi- 

 tion to the compound ganglion of the stellatum. 

 The ganglia to which a single nerve fiber gives 

 >ranches are ordinarily consecutive. But if a gan- 

 jlion contains no nerve cells of a given class, the 

 ibers of this class will ordinarily pass over the 

 ganglion without making connection with it, and 



end their branches to the next ganglion periph- 

 erally which does contain nerve cells of the given 

 class. Stimulation of a preganglionic fiber at any 

 part of its course sets up a nervous impulse which 

 travels to all the branches of the fiber and stimu- 

 lates the nerve cells with which the branches are 



annected. This stimulation peripherally of a fiber 

 }f one or more branches will excite nerve cells 



entrally in one or more ganglia of the point 



animal, that the nucleus of Deiters has no special 

 connection with the eighth nerve, but is situated 

 on the path of the sensory or afferent fibers pass- 

 ing from the spinal cord to the brain. Terrier 

 and Turrer, in 1893, obtained in cases of cerebellar 

 lesion complicated by a lesion of Deiters's nucleus, 

 degeneration of some fibers in the antero-lateral 

 region of the cord on the same side as the lesion, 

 and concluded that the fibers in question were 

 probably derived from the cells of Deiters's nu- 

 cleus. In this view they were supported by the 

 researches of Risieu Russell, while they were op- 

 posed by the conclusions of Marche and Thomas 

 that removal of the cerebellar hemisphere alone 

 without any injury of Deiters's nucleus was fol- 

 lowed by descending degeneration of some of the 

 fibers of the antero-lateral region of the cord. 

 Such fibers had been recognized by Lowenthal as 

 undergoing a degeneration below a hemisection of 

 the upper part of the spinal cord. A further in- 

 vestigation of the subject has been made by R. E. 

 Lloyd, the result of which goes to show that hemi- 

 section of the upper part of the cord is followed 



