LrrKi{.\K\ Notices. iii 



The sympathetic ganglia arise much later than the spinal (at the be- 

 ginning of the second month in man). The thick stem of a spinal 

 nerve divides where it comes in contact with the dorsal margin of the 

 ccelom, giving off" a visceral branch, some fibres of which reach the 

 aorta, while others turn longitudinally, there being no sympathetic cord 

 or ganglia at this stage. Onody(') considers that the sympathetic 

 ganglion originates as an outgrowth from the ventral portion of the 

 spinal ganglia. He believes tliat undifferentiated motile elements 

 wander out of the spinal ganglia and transform themselves into sympa- 

 thelic ganglion cells. The lateral sympathetic ganglia are, in their 

 turn, points of origin for the visceral ganglia. (^) 



His has shown in earlier papers that the olfactory grows from 

 an external ganglion into the brain as do other sensory nerves. 

 The olfactory ganglion adheres secondarily to the olfactory bulb. 

 In all probability, its cells are derived from the epithelium of the 

 olfactory region of the nasal cavity. 



The origin of the eighth fibres is to be sought in the bipolar 

 ganglion cells of the ganglia vestibuli and cochlea?, and of gustatory 

 fibres in the ganglion cells of the glossopharyngeus. 



In the case of the optic nerve the relations are more complicated. 

 From the investigations of Ramon y Cajal it appears that its stalk con- 

 tains fibres springing from the central as well as the peripheral region. 



The neuroblasts of the retina spring from germinative cells which 

 develop near the ventricular surface. The granular layer corresponds 

 to the mantle zone of the medullary plate. 



It appears, therefore, that in the development of the nervous system 

 and sensory organs two forms of cells are differentiated at a very early 

 period — the germinative and epithelial cells. One furnishes the specific 

 elements, the other the frame-work. 



In general, every nerve fibre springs from a single cell. Until the 

 recent observations of Golgi it was supposed that the nervous process of 

 a cell was always unbranched, but Golgi has shown that not only is the 

 axis cylinder provided with processes, but in cells of the second type the 

 axis cylinder divides into a complete mesh-work. Thus the distinction 

 between axis cylinder and other processes of the cell disappears. Yet 

 embryology shows that the former is very distinct from all others in be- 

 ing the first, and for a long time, the only process. The nerve cells de- 

 velop much later in the brain than in the cord. 



The nervous processes continue to grow perhaps for months, and 

 when the blunt end reaches its ultimate terminus it usually divides 

 dichotomously into a cluster of fibrils. In Pacini's and Krause's cor- 

 puscles we have instances where, instead of dividing, the terminus forms 

 an endothelial capsule with soft contents. In another form of end organ, 



1 Cf. A. M. Paterson. On the Development of the Sympathetic System. I'liilos. 

 Trans., iSgo, A. p. 159, as reviewed elsewhere in this number. 



2 Arch. f. Anat. u. Entwickl,, 1885. 



