FORMATION OF THE TISSUES MUCOUS MEMBRANES. 503 



have been observed by Henle, in the gray matter of the brain, which have led 

 him to the belief, that the ganglionic globules or nucleated cells are being 

 continually developed on the exterior, and advance progressively towards the 

 deeper layers, where they replace those which have become disintegrated, 

 and in their turn undergo the same change. The regeneration of Nervous 

 tissue is performed more completely than that of any other that is so highly 

 organized. The degree to which it takes place has been a question among 

 Physiologists ; but many facts, well known to Surgeons, prove that it must be 

 complete. For it will scarcely be denied that the complete recovery of the 

 functions of a Nervous trunk or fibre indicates that the continuity of its com- 

 ponent tubes has been restored ; since all we know of the transmission of 

 Nervous influence leads to the belief that such complete continuity is requisite. 

 In the various operations which are practised for the restoration of lost parts, 

 a portion of tissue removed from one spot, is grafted, as it were, upon another ; 

 its original attachments are more or less completely severed, frequently en- 

 tirely destroyed, and new ones are formed. Now in such a part, as long as 

 its original connections exist, and new ones are not completely formed, the 

 sensation is referred to the spot from which it was taken ; but after an interval, 

 during which it frequently loses all sensibility, its power of feeling is restored, 

 and the sensations received through it are referred to the right spot. A more 

 familiar case is the regeneration of Skin, containing sensory nerves, which 

 takes place in the well-managed healing of wounds involving loss of substance 

 ( 599). A more striking example of regeneration of Nervous tissue, how- 

 ever, is to be found in those cases (of which there are now several on record), 

 in which portions of the extremities that have been completely severed by 

 accident, have been made to adhere to the stump, and have, in time, com- 

 pletely recovered their natural connection with the circulating, nervous, and 

 other systems. The rapid production of Nervous substance in particular 

 cases, is evidenced by Dr. R. Lee's* recent investigations on the nerves of 

 the pregnant Uterus. Not only Nerves, but Ganglia of considerable size, that 

 seem to have no existence under other circumstances, are then apparent. 



The Chemical composition of the Brain has occupied much attention; and the fol- 

 lowing is an outline of the most recent account of it, that of M. Fremy.f In 100 parts 

 of Cerebral matter, there exist 80 of water, 7 parts of albumen (or rather fibrin), and 5 

 parts of fatty matter.! This statement agrees with that of many previous analysts; and 

 it is chiefly with the fatty matter that the attention of Chemists has been occupied. This 

 is stated by M. Fremy to contain, besides the ordinary fatty substances, two peculiar 

 Acids, termed the Cerebric and Oleophosphoric. Cerebric acid, when purified, is white, 

 and presents itself in crystalline grains. It contains a small proportion of Phosphorus; 

 and differs from the ordinary fatty matter in being partly composed of Nitrogen. It is 

 composed of 66-7 per cent, of carbon, 10-6 of hydrogen, 2-3 of nitrogen, 19-5 of oxygen, 

 and 0-9 of phosphorus ; and thus, comparing it with the ordinary fatty acids, contains 

 more than twice their proportion of oxygen. Oleophosphoric acid is separated from the 

 former by its solubility in ether; it is of a viscid consistence; but, when boiled for a long 

 time in water or alcohol, it gradually loses its viscidity, and resolves itself into a fluid 

 oil, which is pure oleine, while phosphoric acid remains in the liquor. The proportion 

 of Phosphorus which this acid contains is about 2 per cent. Cholesterine ( 662) has 

 also been extracted from the brain by M. Fremy, in considerable quantity. On the whole, 

 the proportion of Phosphorus in the brain appears to be about 1 per cent.; a small 

 quantity of Sulphur is also present. The proportion of Fixed Salts is small, being not 

 above 3 parts in 100 of dry Cerebral matter; which is less than half the proportion 

 that exists in Muscle. 



* Proceedings of the Royal Society, June 17, 1841 ; and Phil. Trans. 1841, Part ii. 



j- Graham's Chemistry [Am. ed., p. 713]. It is there stated that the analytic method of 

 M. Couerbe was very defective. 



$ According to Lassaigne, the chemical composition of the Cortical and Medullary 

 substance is essentially different; the former containing much more water than the latter, 

 and little colourless fat, but nearly 4 per cent, of red fat, which does not exist in the other. 



