THE NERYOUS SYSTEM. 465 



oxalic acid, which, is frequently deposited in combination 



Fig. 124.* Fig. 125. f 



with lime (fig. 125) as an urinary sediment. Like cystin, 

 but, much more commonly, it is the chief constituent of 

 certain calculi. 



A small quantity of gas is naturally present in the urine 

 in a state of solution. It consists chiefly of carbonic acid 

 and nitrogen. 



CHAPTEE XVI. 



THE NERVOUS SYSTEM. 



The nervous system consists of two portions or con- 

 stituent systems, the cerelro-spinal and the sympathetic or 

 ganglionic, each of which (though they have many things 

 in common) possesses certain peculiarities in structure, 

 mode of action, and range of influence. 



The cerelro-spinal system includes the brain and spinal 

 cord, with the nerves proceeding from them, and the several 

 ganglia seated upon these nerves, or forming part of the 



* Fig. 124. Crystals of oxalate of lime, 

 f Fig. 125. Crystals of cystin. 



HH 



