ARRANGEMENT OF THE NERVE FIBRES. 



209 



mouth, in the papillae fungiformes and circumvallatae of the 

 tongue, in the glans penis and clitoridis. The discoverer 

 also found them in not inconsiderable extension in mam- 

 mals. 



Let us take the sclerotic conjunctiva of a calf's eye (Fig. 

 181), and follow the course of the nerve 

 through the separated mucous membrane. 

 After a long interval, we meet in the first 

 place (*) with a dichotomous division of 

 the double contoured nerve fibre (c). 

 Then, after following the branch for a 

 shorter or longer distance, we arrive at a 

 striking appearance (a). It is an elongated 

 oval, occasionally slightly bent body, 

 measuring 0.075 1 to o. 1409 mm. in its 

 greatest diameter, and about one-third as 

 much in its transverse. In man and the 

 ape, the structure has a globular form, ac- 

 cording to Krause. 



Let us return to the calf. We here 

 meet with a dull, nucleated, moderately 

 thick envelope, with an enclosed hyaline, 

 homogeneous, rather thick fluid contents. 



The primitive sheath of the nerve trunk 

 gives off its neurilemma to this mem- 

 brane, or, to express ourselves more intelli- 

 gibly perhaps, it increases in thickness 

 and becomes the parietes of the terminal 

 bulb. 



At the first cursory examination, one might suppose that 

 the nerve fibre had thus terminated. One would, however, 

 be very much deceived ; for, after losing its medullary 

 sheath, the most important constituent of the nerve fibre, 

 the axis cylinder, passes through the structure to end at 

 the opposite pole, occasionally with the slightest intumes- 

 cence. 



This is the terminal bulb, so far as I am familiar with it. 



Fig. 181. — Terminal bulb 

 from the conjunctiva bulbi 

 of the calf; «, terminal bulb; 

 c, nerve fibre, branching at*; 

 i, axis cylinder. 



