THE NERVOUS SYSTEM. 359 



for the present abstain from any definite opinion. The processes of the 

 nerve-cells, in the brain and spinal cord, which were first noticed by 

 Purkinje, will be more minutely described when we come to speak of 

 the central organs, and the question will there be discussed as to their 

 relation to the central fibres. In the ganglia, there are no cells with 

 branched processes, instead of which we find only those with one, two, 

 rarely three or four, pale appendages, which are continuous with dark- 

 bordered tubes. The nerve-cells consist, for the most part, of a coagu- 

 lated, although soft protein-compound, which appears to correspond very 

 closely with that of the axis-fibres. It has not been ascertained whether 

 the membranes and nuclei differ essentially from it. The fatty matter, 

 which has also been found in small quantity in the gray substance, con- 

 stitutes in every case the opaque granules in the cells, and appears to 

 exist in other conditions also, in their contents. When isolated nerve- 

 cells are compressed, they become much flattened, resuming their pris- 

 tine form when the pressure is removed. Their processes also are very 

 elastic, and like the axis-fibres may be considerably extended, and after- 

 wards again retract themselves. 



As our knowledge of the chemical composition of the gray and white 

 substance still leaves much to be desired, I content myself with the fol- 

 lowing statements. Lassaigne, in the brain of a lunatic, found — 



Gray substance. White substance. 



Water 852 73 



Albuminous matter ...... 7-5 99 



Colorless fat ....... 10 13-9 



Red fat 3'7 09 



Osmazome, lactates ...... 1'4 i'O 



Phosphates 1-2 1-3 



According to Fremy (Comptes rendus, tom. ix. p. 703, "Ann. d. 

 Chem. und Pharm. 1841," vol. xl. p. 69), the brain (both substances 

 together) contains — 



Water 80 



Albumen .......... 7 



Fatty matter ......... 5 



Osmazome and salts ........ 8 



100 



Which almost exactly agrees with Vauquelin's analysis, who more- 

 over estimates the osmazome at 1*12, and the salts at 6-65; whilst it 

 differs from that of Denis, who found much more fatty matter (12-40 

 in a man 20 years old, 13-3 in one aged 78), and less water (78 and 76[}). 



CENTEAL NERVOUS SYSTEM. 



§ 112. Spinal Cord. — The nervous elements are so disposed in the 

 spinal cord, that its external, white substance is constituted almost ex- 



