y 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 b}- 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 cenical 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 Nenous 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 ner\-e 

 cells in the inferior horns of gray matter, is made veiy 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, ner\-e 

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



* Ueber den Bau des Centralen Nenensystems der Schildkiote. p. 53. 

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

 largements of the frog's spinal cord. 



