2 The Structure of the Spinal Cord of the Ostrich 



ted to various parts of the cord, as, for example, the study of DuvaV 

 concerning the Sinus rhomboidalis, and an experimental work of Fried- 

 lander* on the fibre tracts. To these may be added also the works of 

 Singer, MiXnzer, and others who devoted themselves more particularly to 

 the brain. It is, further, not to be forgotten that the studies of Retzius, 

 Ramon-y-Cajal, van Geliuchien, and v. LenliosseJc concerning the nerve- 

 cells and fibres of the spinal cord in Golgi preparations were carried out 

 largely on the chick. No attention, however, seems to have been directed 

 toward the spinal cord of the ostrich. A cross-section, apparently of the 

 thoracic region, is pictured by Edinger^ but is not otherwise described. 

 The material on which this study is based consisted of three ostrich 

 spinal cords taken from the neurological collection of the Anatomic. 

 Two were practically intact; the third had been cut into segments. All 

 three had been hardened in formol. After the macroscopic examination 

 was completed, series of transverse sections were made in all segments. 

 Unbroken sagittal and fronto-longitudinal series were prepared through 

 three segments of the lumbar enlargement, and a fronto-longitudinal se- 

 ries of one segment in the cervical region. Sections were also prepared 

 of a decalcified vertebra showing the cord in situ with its membranes, the 

 nerve roots, and spinal ganglia. Where other than the usual stains were 

 used they are specified in the text. 



The Meninges. 



The cord is supported in the vertebral canal by a connective tissue 

 sheath which, like that in mammals, may be described as consisting of 

 three separate membranes or envelopes. In order, from within outwards, 

 they are the pia, arachnoidea, and dura. These structures are repre- 

 sented in Fig. 1. 



Of the three envelopes the dura is by far the strongest. It is this 

 that forms the tough fibrous sheath surrounding the cord, which one 

 sees on the removal of the latter from the vertebral canal. It consists 

 of a membrane .011 to .012 mm. thick, made of thickly-lying coarse fibres, 

 a.nd contains no blood-vessels. Outside the dura is a connective tissue 

 layer which lines the vertebral canal, and forms the periosteum of the 

 vertebrse. This, having the same histological character, may be described 



^ Duval, Recherches sur le Sinus Rhomboidal des Oiseaux, Journ. de I'Anat. 

 et de la Phys., 1877. 



* Friedlander, Untersuch. iiber das Riickeninark und das Klelnhirn der 

 V6gel, Neurolog. Centrabl., 1898. 



"Edinger, Nervose Centralorgane, 1900, p. 76. 



