758 A. SUBDA llAU AND P. II. JOHNSON ON THE NERVOUS 



down almost to a single row of cells. In their final stages their 

 cellular character disappears by migration of the cells to the 

 secondary chain, and a fibrous connection is left (text- fig. 11). 

 With the exception of certain connections which are maintained 

 with the chief plexuses of the trunk, these also ultimately dis- 

 appear, usually after the appearance of the definitive rami. 

 These last are from the beginning purely fibrous. Their develop- 

 ment consists merely of a growth in length, as the secondary 

 sympathetic ganglion moves away from its early position at the 

 point of union of dorsal and ventral roots. The range of move- 

 ment varies in different regions, being very small in the neck. 

 Thebault (14) figures the rami commimicantes of Corviis as some- 

 times quite distinct in the neck region, but also describes a fusion 

 of the sympathetic ganglion with the spinal nerve, and remarks 

 that all the intermediate stages may be found. A ramus coin- 

 municans can always be found in our material by microscopic 

 examination. 



That the sympathetic ganglion, while making its own contri- 

 bution to the mixed spinal nerves, carries with it fibres from 

 both roots, has been abundantly proved by previous observers. 

 Rossi (16), in his recent paper on the afferent paths of the 

 sympathetic system, demonstrates by direct anatomical observa- 

 tions, that cells occur in the dorsal root ganglia which send their 

 processes into the rami communicantes. These he regards as the 

 cells of origin of Kolliker's fibres, and considers them to be 

 afferent sensory neurones. 



G. The Suprarenal Bodies. 



Our observations lead us to agree with those who ascribe to 

 these bodies a dual origin : e. g. Balfour, Poll, Mitsukuri, Gia- 

 comini, and Goormaghtigh. 



In Sparrow 7 (= 78-hr. chick), text-fig. 13, there are already 

 signs of the grooves in the coeloraic epithelium from which the 

 cortical portion of the suprarenal bodies will arise. These 

 grooves are situated on either side of the mesentery and close to 

 it. Laterally to them will be found the internal Wolffian vein 

 and the mesonephros, and in certain cases the external glome- 

 rulus of the pronephros can also be seen. In text-tig. 14 these 

 relations are clearly visible, and the proliferation of cells has 

 already started at the region described. The cells of the ca^lomic 

 epithelium are cubical with large nuclei. Mitotic figures are 

 numerous and the products of division apjiear to be moving 

 inwards. In Sparrow 8, text-fig. 15, the proliferation of cells 

 becomes more marked, and a ridge is formed internally. These 

 cortical primordia appear to be metamerically arranged. In 

 Sparrow 11, text-fig. 16, the cortical primordia are very clearly 

 marked, but still closely attached by a broad base to the ccelomic 

 epithelium. Gi'oups of cells appear to be moving towards their 

 later position between the aorta and the mesonephros. 



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