68 Dixon—On the Development of the Branches of the Fifth Cranial Nerve in Man. 
Summary. 
1. Before the ophthalmic nerve is present in the embryo,.a cellular cord 
stretches upwards and forwards from the Gasserian ganglion, and occupies the 
place of the future nerve. This is easily demonstrated in the rat, and a similar 
condition appears to prevail in the human embryo. 
2. Axis-cylinder processes grow out from the cells of the Gasserian ganglion 
into this cellular cord, and in this manner the ophthalmic nerve is formed. 
3. The axis-cylinder processes increase in number, while the cells of the 
original cord become fewer, and at the same time become disposed around the 
developing nerve. 
4. The first formed ophthalmic trunk corresponds to the nasal nerve of 
the adult. 
5. The frontal nerve is formed later, and its proximal part in man is united 
in a common trunk with the proximal part of the nasal nerve. In the rat, 
however, the nerves in the first instance, take separate origin from the Gasserian 
ganglion. 
6. In mammals no outlying part of the Gasserian ganglion is present as a 
ganglion either for the ophthalmic or nasal nerve, in the sense of a ganglion of a 
posterior nerve root. 
7. A single undivided Gasserian ganglion gives rise to all three divisions of 
the fifth nerve. 
8. In the beginning of the sixth week all the important branches of the 
ophthalmic nerve of the adult are represented in the embryo. 
9. The fourth and frontal nerves are from an early period closely connected. 
10. The ciliary ganglion is first recognizable as a distinct cellular mass at the 
beginning of the sixth week. 
11. The ciliary ganglion appears, in the first instance, to be more closely 
connected with the frontal and fourth nerves, than with the nasal and third 
nerves. 
12. Later this ganglion shifts its position, and in the eighth week it has 
established the connections, and assumed the situation, that obtains in the adult. 
13. The ciliary ganglion can in no sense be the homologue of a spinal 
ganglion. 
14. The superior maxillary nerve appears as an independant branch of the 
Gasserian ganglion, in the embryo of four weeks. 
