MORPHOLOGY OF EYE MUSCLE NERVES 



25 



ponents: a short process and the long undifferentiated protoplasmic 

 strand or bridge with which it is apparently fused so as to give, in spe- 

 cimens stained by certain methods the appearance of a single long 

 process. In plate 23, figure 1, one of the bridges is represented, the 

 proximal side of which has fused with the matrix of the cord while the 

 distal is united Avith that of the myotome. (See text-figure A.) 



A similar condition is also depicted in figure 2. At later stages 

 one may find connections present between the cord and group of cells, 

 which eventually form the spinal ganglia, and between the latter and 



Text fig. A Taken from Paton's figure 2, plate 2.3; my., myotome; neur., 

 neuraxon (neurofibril, Paton) ; rx.v., anlageof somatic motor nerve (plasmodesma, 

 Paton); scl., sclerotome (myotome, Paton); th.n., neural tube, Paton's figure 1, 

 plate 23, is in all essentials like this, but does not show the neuraxon process 

 (neurofibril) stained. 



Text fig. B Taken from Dohrn, 1907, figure 7, plate 21; my.,- VanWijhe's 

 second myotome (m.obl.sup.); ir'ch.a., peripheral chiasma of the trochlearis; 

 tr'ch., trochlearis anlage; vs.opt., optic vesicle; V. opt.su., ramus ophthalmicus 

 superficialis trigemini; VII.opt.su., ramus ophthalmicus superficialis facialis. 



the periphery. Further there is abundant opportunity to study these 

 plasmodesmata (Held) in the region of the cranial nerves, where un- 

 differentiated links of protoplasm frequently unite the existing gan- 

 glionic masses either with the central nervous system or with the pe- 

 riphery. In the case of the oclomotorius and trochlearis the existence 

 of these bridges is very problematic. 



The present writer ('03) made the attempt to discover whether 

 the protoplasmic bridges of Paton were primary or secondary 



