THE NERVES. 67 



tinuous with similar fibrillse, of which, under high powers, the apparently 

 granular contents of the cell are found to be composed, and which appear 

 therefore simply to run through the cell. The fibrillae may be, and probably 

 are, primitive nervous fibrils, but they are so delicate, that it has not as yet 

 been found possible to ascertain their destination. With regard also to the 

 axis-cylinder which is seen proceeding out of the ganglionic corpuscle, although 

 it is highly probable that it originates in that corpuscle, the fact has not been 

 proved nor has its relation to the nucleus of the corpuscle been demonstrated. 

 In fine, all that is known on the subject is, that many of the fibrillas and axis- 

 cylinders can be shown either to originate in or to pass through ganglionic 

 corpuscles (or nerve-cells), and other nerves can be shown to contain such 

 nerve-cells in their anterior at certain parts of their course. But whether in 

 the case of such connection in one of the central organs the cell' is to be 

 regarded as the origin of the nervous fibril, or whether the fibril merely passes 

 through the cell (as some observers believe), just in the same manner as nerves 

 pass through ganglia, has not been determined. If the latter view be correct, 

 it may be that nerves have really no central termination, but that their fibrils 

 start from their peripheral distribution, travel to the nervous centre, are there 

 brought into connection with the nerve-cells, and thence return to their distri- 

 bution. However, in the present state of anatomical knowledge, the more 

 probable opinion seems to be that which is usually entertained, viz., that each 

 nerve-fibre is connected somewhere with a gauglionic corpuscle, which is to be 

 regarded as its central termination or origin. Dr. Beale asserts, that even in 

 those ganglion-cells, which appear either altogether destitute of processes, or 

 unipolar, numerous fibres can be seen proceeding out of them if the proper 

 reagents be used and very high powers employed. 



The peripheral connections, or terminations of the nerve-fibres, are some- 

 what more easy to ascertain, though even as to these a great difference exists 

 with respect to minute details. They are usually and naturally studied in the 

 sensory and motor nerves separately. 



Sensory nerves sometimes terminate in minute plexuses in the subcutaneous 

 or submucous areolar tissue. Dr. Sharpey says that he has seen the ultimate 

 fibres of these minute plexuses come into close contact with the connective- 

 tissue corpuscles, but has not been able to trace any distinct connection between 

 them. 



The white substance of Schwann and the tubular sheath usually disappear 

 as the nerve approaches its termination, leaving only the axis-cylinder invested 

 by its proper basement-membrane, on which nuclei can be seen at intervals, 

 and in many cases the axis-cylinder itself breaks up into the primitive fibrils. 

 In some parts, however, the fibres appear to be inclosed up to their termination 

 in a sheath, which is either a prolongation of the neurilemma, or a continuation 

 of the tubular membrane. The differences of opinion prevailing on the ques- 

 tion of the ultimate distribution of the nerve-fibres depend on their extreme 

 delicacy and the consequent great difficulty of following individual fibres in 

 continuity. Hence what some observers describe as a free end, in which the 

 nerve terminates, others regard as merely a bending of the fibre where it be- 

 comes lost to sight, or a spot where it is lost sight of in consequence of the 

 power used being too low, or from difficulty in focussing. These ultimate 

 fibres, it should be remembered, are structureless, and can therefore only be 

 recognized positively as nervous by their continuity with a nerve of more 

 complex structure. 



In the papillaD of the skin, or mucous membrane, and on the surface of various 

 membranes (conjunctiva, mesentery, &c.), three different kinds of terminal 

 organs have been found connected with the nerves, viz., the end-bulbs of Krause, 

 the tactile corpuscles of Rudolph Wagner, and the Pacinian corpuscles. 



The end-bulbs of Krause are small capsules of connective tissue, in which 

 nuclei can be detected by reagents, and in which one or more nerve-fibrils 



