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VII. Development of the Sympathetic Nervous System in Mammals. 
Jiy A. M. Paterson, M.D., Professor of Anatomy in University College, Dundee. 
Communicated by A. Milnes Malishall, F.R.S. 
]{eceived April 18,—Read Maj 1. 1890. 
[Plates 22-30]. 
I. Introduction. 
The Mammalian sympathetic nervous system presented a})|)arently insurmountable 
obstacles to both anatomists and physiologists till the publication of Gaskell’s 
Monograph in 1885 (1). Our knowledge of its structure and functions is now, 
however, placed on a much firmer basis ; and it is possible to enter seriously into a 
consideration of its morphology and development. 
A. Physiology. 
Tiie cells composing the ganglia in the main sympathetic chain are shown by 
Gaskell to be trophic only. They are neither automatic nor reflex in their action, 
but merely nourish the fibres which pass from them centrally or peripherally. Tlie 
gray Rami communicantes spring from the ganglia and are distributed as trophic 
fdires to the roots and trunk of each spinal nerve and their meninges, and the 
bodies of the vertebrie. In some cases [e.g. fore and hind limbs) the vasomotor fibres 
reach their destination through these Pami. The white Rami communicantes are 
only found in two regions. In the Uog between the tenth and twenty-fifth spinal 
nerves (second dorsal—second lumbar), and in the Kami of tlie second and third 
sacral nerves. This corresponds fairly accurately with their distribution in the 
liuinan subject (2). In botli regions they cous^ist of very small medullated fibres 
( l'8/r to 2'7/x). In the anterior region the white Pami pass from the spinal nerves 
to the ganglia, and tliere separate into two gronps ; one set forms vasomotor fibres, 
which join the ganglia, become connected with the ganglion-cells, and are distributed 
peripherally as gray fibres, greatly increased in numbers. The othei' set does not 
join the ganglia, but, passing over them, forms the nerves distributed in the Splanch- 
nics to the abdominal viscera as visceroanidhitory fibres. In the posterior region 
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