378 THE POPULAR SCIENCE MONTHLY. 



sal regions, and of a bundle of medullary fibers, which arise in 

 the ventral portions of the brain and pass out from it immediate- 

 ly below the entrance of the ganglionic fibers. Evidently there 

 are two roots, which, from their close juxtaposition, have been 

 hitherto unrecognized ; the ganglionic bundle is the true dorsal 

 root, the medullary bundle the lateral root. If, now, we modify 

 Bell's law by saying that all medullary fibers are efferent or mo- 

 tor, and all ganglionic fibers afferent or sensory, we can under- 

 stand the double function of the facial nerves and of the other 

 nerves resembling it to wit, the trigeminal, glosso-pharyngeal, 

 and vagus. 



The recognition of the lateral root as distinct from, though 

 joined with, the dorsal sensory root, removes many obscurities in 

 the anatomy of the nervous system. We know that lateral roots 

 are not confined to the nerves of the head, but they also occur in 

 the upper cervical nerves, and I regard it as highly probable that 

 with the progress of research they will be found sharing in the 

 formation of other spinal nerves. Should this expectation be ful- 

 filled, the long-established conception of the posterior roots as 

 purely sensory will have to be modified, although it has reigned 

 for three quarters of a century as one of the fundamental concep- 

 tions of physiology. 



THE THIRD DISCOVERY. The third discovery is that neither 

 the nerve cells nor nerve fibers are directly continuous either with 

 other nerve cells or with the cells or structures of other tissues 

 and organs. Every nerve cell, together with its fiber, is an entity, 

 and is not organically continuous with anything else. It is cer- 

 tainly premature to affirm this discovery positively, for we can 

 say at present only that the consensus of the best opinion, of such 

 men, for instance, as His and Kolliker, is in favor of the concep- 

 tion that every nerve cell plus its nerve fiber is an isolated ele- 

 ment. Until recently the hypothesis was received with favor that 

 the cells of brain and spinal cord were connected by threads of 

 protoplasm, or, to speak more precisely, by branches of the pro- 

 cesses of the cells ; according to this hypothesis, there would be a 

 direct protoplasmatic continuity between the different parts of 

 the nervous system, and therefore a nerve impulse brought by a 

 sensory fiber to the brain could be conceived as traveling along 

 an uninterrupted pathway of living matter until it produced its 

 final action. In many text-books of physiology there are dia- 

 grams to illustrate the theory of a continuous pathway. It is evi- 

 dent that if there is no such connection between nerve cells as 

 assumed, then we must radically alter our conceptions of the 

 process of the transmission of nerve force through the brain. 



In the question before us, Camillo Golgi and his followers 

 must lead the way. Golgi, whom the world will probably rank 



