7 CENTRAL NERVOUS SYSTEM. 



side what Stieda names, in turtles, the "central longitudinal bundle of 

 the medulla oblongata."* The comparative importance of this bundle 

 in different regions of the cord, is shown in Plates XI. XII. & XIII. 

 It forms a conspicuous part of sections from the alligator, iguana, helo- 

 derma, skink and anolis. 



Plates I. IV. & XXIV. are referred to as suggesting that in rep- 

 tiles with bodies shielded by bony plates or thick scales, the fibres of the 

 superior columns, compared with those of the inferior columns, are rel- 

 atively smaller than in naked reptiles ; and also as illustrating the fact, 

 noted by Gerlach for the human spinal cord, that the fibres, which form 

 the infero-lateral columns, are, as a whole, larger in the cervical than 

 in the lumbar region. 



The depressions in the outline of the lateral columns seen in Plates 

 I. & V. for example, correspond with the position of the lateral ligament, 

 recently described by me, the structure of which in ophidians, is shown 

 in Plates XIV. & XV. See Journal of Nervous and Mental Disease, 

 Vol., VIII, No. 3, July, 1881. 



The mode of exit and the course of the inferior root-filaments are 

 well shown in Plates III. & IV. and their relation to the large nerve 

 cells in the inferior horns of gray matter, is made very apparent in Plates 

 XVIII. XXXI. & XXXIII. 



Plate XIV. ii shows the characteristic mode of exit of the superior 

 roots in ophidians, and Plates XXVI. & XXXVI. show the arrange- 

 ment of the same parts in the brachialf region of the frog. 



The gray substance of the spinal cord is composed of fibres, nerve 

 cells, connective tissue and blood vessels. Its position is central to the 



* Ueber den Bau des Centralen Nervensystems der Schildkrote. p. 53. 

 t The terms, 'brachial' and 'crural' were used by Wyman to designate the en- 

 largements of the frog's spinal cord. 



