42 OLOF LARSELL 



parts of the vascular system, seems to justify the assumption 

 that they are sensory in function. 



The thu'd type of ending to which reference was made was 

 found among the epithehal cells hning the mucosa of the nasal 

 septum. These endings consist of very dehcate arborizations 

 which pass between the colmnnar cells of the epithehmn and 

 approach the surface of the membrane (fig. 30). They are ter- 

 minal twigs of fibers which appear to be unmyeUnated. These 

 fibers, as shown in the figure, approach the epitheliima in small 

 strands of three or four fibers to spread out at its base, where 

 the terminal threads which form the free end fibers are given 

 off. No varicosities or end-knobs were seen. 



Such terminations are present in both sensory and respiratory 

 regions of the septal mucosa and in the epithehmn of the vomero- 

 nasal organ. Smiilar endings, but with varicosities or end- 

 knobs, have been described and figured in these regions by von 

 Brunn ('92), von Lenhossek ('92), Retzius ('92), Cajal ('94), 

 Read ('08), and others. Most of these writers tend to ascribe 

 them to the trigeminal nerve, although von Lenhossek suggests 

 the possibility that they represent olfactory fibers whose cells 

 of origin do not have the same position as others, but lie within 

 the centripetal olfactory tract, enclosed in the course of the 

 oKactory bundle. 



Figure 31 represents what appears to be the centripetal con- 

 tinuation of a fiber which gives rise to free endings such as those 

 just described. This figure was drawn from a section which lay 

 just below the epithelium, in a sagittal series through the nasal 

 septmn. As shown in the figiu^e, the fiber (fi) divides at its 

 extremity into four slender twigs which appeared as if they had 

 been cut near their tips. Centripetally this fiber unites with a 

 similar one (fi'). The nerve process of which these fibers are 

 branches is part of a small bundle (p.pL) which fonns a portion 

 of the terminalis plexus of the nasal septmn shown in figure 4. 



While the fibers which temiinate in the manner indicated re- 

 semble in size and distribution those of the nervus tenninalis, 

 there remains the ^possibility that they are the continuation of 

 the more delicate threads which are present in the nasopalatine 



