NERVES OF THE CONJUNCTIVA. 457 



and physiological importance. On the other hand, in regard 

 to the higher animals, the Mammals, and Man himself, the 

 opposite relation to that of the Frog holds, and the upper 

 lid is more richly supplied with nerves than the lower. 



Finally, in regard to its origin, the internal medial trunk 

 is to be regarded as one of the terminal branches of the infra- 

 trochlearis, and the lateral as the termination of the nervus 

 lachrymalis, both of which proceed from the first branch of 

 the trigeminal nerve. 



After forming the coarse-meshed plexus in the subcoa- 

 junctival, and in the deeper layers of the conjunctival tissue, 

 the nerves, continually becoming smaller till they are com- 

 posed of only a few fibres, gradually pass forwards. These 

 branches never exhibit any plexiform anastomoses. The 

 relation of the smallest trunks, which are still composed of 

 from two to three doubly contoured fibres, is in some animals, 

 as, for example, in the Frog, so regular that it may here be 

 minutely described. After the trunks of the last order have 

 extended as far as to the plane just beneath the last layers of 

 the vascular capillary plexus, division once more occurs, owing 

 to which the still doubly contoured fibres, as they part from 

 each other, run in a direction nearly at right angles to that of 

 the trunk, and may be followed for considerable distances, 

 maintaining a perfectly straight course, or being but slightly 

 sinuous. A system of more or less parallel doubly contoured 

 fibres is thus produced, which lies beneath the capillaiy net- 

 work. In other animals the course and mode of division of 

 the ultimate trunklets composed of doubly contoured fibres is 

 less regular ; and it is only necessary to state that, rising above 

 the vessels in the most diverse vertical oblique direction, they 

 gradually reach the surface, where, in the last division of the 

 dark fibres, their transition into non-medullated fibrils takes 

 place. An exception to this is met with in certain fibres which 

 only gradually ascend, as Helfreich satisfied himself, not in 

 surface preparations, but in a considerable number of vertical 

 sections in various animals. In this case a single fibre 

 proceeds from a trunklet that is still composed of a large 

 number of doubly contoured fibrils, and runs nearly in the 

 middle of the matrix of the conjunctiva ; the fibre at this point 



