io 4 R. J- ANDERSON [august 



many words. Owen's typical vertebra, it will be remembered, has 

 growths above, below, and at the sides. The two dorsal growths end 

 in the spine ; the lateral growths are the transverse processes (dorso- 

 lateral), and the lower growths (ventro-lateral) may join the ribs which 

 form an arch like the dorsal one. The limbs are represented by 

 diverging appendages. The limb folds seem to partake of the quadri- 

 lateral symmetry type in some fishes. Humphry pointed out that the 

 term " duality " is inapplicable to the nervous system and skeleton. 

 The lineal axis of the embryo sends off the processes referred to, and there 

 is therefore a quadrilateral rather than a bilateral symmetrical arrange- 

 ment. 1 Humphry, however, distinguished between the body as a whole 

 in this regard and the separate parts. Leaving out the bodies of the 

 vertebrae which are variously formed, but originally developed round 

 an endodermic growth, one can make out a radiate symmetry of four, 

 five, or six rays, according as certain processes are counted or omitted. 

 The pillars of the dorsal arch may be counted separately, so may the 

 transverse processes and body processes ; or, reckoning each pair as one 

 process forming a two-pillared arch, there are four arches. The spinal 

 nerve cord section occupies the dorsal arch, the sympathetic the ventral, 

 and the posterior root ganglia are at the sides. It is clear, however, that 

 the spinal cord may be looked upon as made up of two lateral halves, 

 so may the sympathetic cords. A survey of the entire system tends 

 to render the bilateral symmetry of each less clear, whether taken 

 together or separately. The sympathetic seems to be of more con- 

 siderable relative importance in early life, judging from the drawings of 

 Paterson. The ganglia are often large in man, but the size appears to 

 be due in the abdominal ganglia to fibrous tissue (D. J. Cunningham). 

 W. Alexander has removed the superior cervical in man with advantage 

 to the patient, proving how far the system has gone back. 2 The sympa- 

 thetic is, however, of enormous interest because of its distribution, 

 subsidized by the spinal, in the viscera and arterial coats. The symmetry 

 that takes account of the spinal cord, divided into two equal lateral 

 parts, has also reference to the division of the abdominal nervous system, 

 so that a modified quadrilateral symmetry may appear as a bilateral 

 symmetry. The dorsal and ventral systems, as every one knows, are 

 mainly independent of one another. The presence of the serous mem- 

 branes secures this independence in part, but the nerve connections do 

 not favour a ready transference of impressions from one system to the 

 other. The connections, however, come into use often in disease, and 

 a slight activity in the terminals of either systems, may produce a 

 profound disturbance in the district supplied by the other. The sym- 

 pathetic ganglia associated with the cerebral system are obscured by the 

 magnitude of the large brain and its connections in vertebrates. The 



1 See Quain's "Anatomy," 8th ed. 



2 Nerve cells being now proved to be trophic only, the fibres collectively assume more 

 prominence in our estimate of the value of a nerve tract, or district. 



