Herrick, Aneticephalus and Amyelus. 3 



same relations as the sciatic nerve. Cutaneous nerves medul- 

 lated in their superior courses and everywhere near the skin ; 

 nervous termini within the muscles, a bundle enters into the 

 deeper layer of the M. tibialis and ends in a plaque, resembling 

 the termini of the peripheral motor fibres in the striated mus- 

 cles. To admit that this bundle is motor, would be contrary 

 to our actual knowledge, and the facts mentioned are moreover 

 not sufficient to support this supposition. Posterior roots prob- 

 ably without myelin ; optic nerve destitute of nervous elements ; 

 retina with neither ganglion cells nor nerve fibres ; texture of 

 the sympathetic ganglia normal. 



A review of these facts leads us to the following important 

 conclusions : 



(/) The development of the peripheral sensory nervous system 

 does not depend upon the central nervous system, since the former 

 can occur and develop progressively in the total absence of the ence 

 phalon and even of the spinal cotd. 



(2) The peripheral sensory nerve fibres originate from cells of 

 the spinal ganglia and are the prolongations of their axis cylinders; 

 for this reason we ought to look upon the cells of the spinal gangli- 

 on as a primary nucleus {Zcllencomplex), as a vet it able nucleus of 

 sensoty fibres. 



The cells of the spinal ganglia have for the sensory fibres 

 the same importance as the motor nuclei of the brain base and 

 the cells of the ventral cornua of the cord have for the motor 

 nerves. The works of Kolliker, His, Ramon y Cajal and Len- 

 hossek, as well as the author's own researches, enable us to af- 

 firm that the sensory fibres do not have central nuclei, a fact of 

 great general importance which may be observed not only in 

 the peripheral sensory fibres and in the dorsal spinal roots, but 

 also in the sensory roots of the cranial nerves, as His has shown 

 in his " Gangliennerven des Kopfes. " So likewise we are 

 obliged to regard the cells of the retina from which the optic 

 nerve arises as the ganglion of the optic nerve. Pathological 

 researches, the method of v. Gudden, the results of Ganser 

 who brought about the atrophy of the ganglion cells of the reti- 

 na by extirpation of the tractus opticus, the histological re- 



