588 



NERVOUS SYSTEM. (NERVOUS MATTER.) 



in contact with soda, potass, and ammonia, it 

 immediately gives soapy compounds. It forms 

 compounds insoluble in water with other 

 bases. M. Fremy has observed a remarkable 

 transformation of oleo-phosphoric acid. When 

 boiled for a long time in water or alcohol, it 

 gradually loses its viscidity and becomes a fluid 

 oil, which is pure elaine, while the liquor con- 

 tains phosphoric acid. This decomposition be- 

 comes very rapid, when the liquor is rendered 

 slightly acid. Although M. Fremy's attempts 

 to form this acid directly, by uniting elaine and 

 phosphoric acid, were unsuccessful, he still 

 deems it probable that this acid may consist of 

 the elements in question and be analogous to 

 the compound of sulphuric acid and elaine, or 

 sulph-oleic acid. It contains from 1.9 to 2 per 

 cent, of phosphorus in the condition of phos- 

 phoric acid. 



M. Fremy also finds, as Couerbe had previ- 



Albumen 



Cerebral fat 



Phosphorus 



Osmazome and salts .... 

 Water 



ously done, that cholesterine may be extracted 

 from the brain in considerable quantity. He 

 obtains it by boiling the ethereal product in 

 alcohol rendered strongly alkaline by potass. 

 A cerebrate, an oleate, and a phosphate of pot- 

 ass are thus obtained, with glycerine and cho- 

 lesterine. On cooling, the alcohol deposits the 

 cerebrate and phosphate of potass and the cho- 

 lesterine ; and in treating the deposit by cold 

 ether, we remove all the cholesterine, which 

 maybe purified by subsequent crystallizations. 



In preparations of the brain, preserved in 

 spirits, a substance of crystalline character, 

 which resembles cholesterine, is apt to form 

 round the piece. 



The quantity of phosphorus varies conside- 

 rably in different periods of life, and is greatly 

 diminished in idiotcy. The following table 

 from some analyses of L'Heritie will illustrate 

 this statement. 



100.00 10000 100.00 100.00 100.00 



From these comparative analyses it appears 

 that the minimum of phosphorus exists in in- 

 fancy, in idiotcy, and in old age; and that the 

 maximum of water is found in the infant. This 

 latter fact is of practical interest, and affords 

 some explanation of the greater tendency to 

 liquid effusions in early childhood than in more 

 advanced life. 



Nervous actions. In order to offer a clear 

 explanation of the working of the nervous sys- 

 tem, it will not be amiss to quote a few ex- 

 amples of actions effected through its instru- 

 mentality. 



Let me, however, first remark, that as the 

 mind is connected more especially with the 

 nervous system, so that system becomes the 

 channel of its mandates, as well as of impres- 

 sions conveyed to it. But there can be no 

 doubt that the nervous system can act inde- 

 pendently of the mind, and that certain actions 

 which need the intervention of nerves and ner- 

 vous centres, are accomplished without the 

 consciousness of the individual, and some- 

 times in spite of his Will. 



It seems, therefore, a correct, as it is cer- 

 tainly a convenient arrangement of nervous 

 acts, to divide them into those in which the 

 mind is concerned, either as an agent or as a 

 recipient, (mental nervous acts,) and into those 

 which result from mere modifications in the 

 nervous matter, quite independent of mental 

 interference (jj/ii/sictil nervous acts). 



Let me illustrate this division by examples. 

 Any ordinary act of the will, the voluntary 

 movement of the arm lor instance, is effected 

 by a mechanism to which the first impulse is 

 given by a change in the mind; 1 will to move 

 my arm ; this mental change affects the nerves 

 of the arm, which excite certain muscles to act. 



That the nerves are the channels for conveying 

 this influence of the will is proved, beyond all 

 doubt, by experiment and disease. If their 

 continuity with the brain be injured, the power 

 is necessarily lost, although the will itself con- 

 tinue unimpaired 



WeJ'eel through the instrumentality of the 

 nerves. In writing, I am conscious, through 

 the sensibility of my fingers, that 1 hold a pen 

 in my hand. Were that sensibility destroyed, 

 although the power of holding the pen re- 

 mained, 1 should lose the consciousness of its 

 presence between my fingers, and they would 

 cease to grasp it. This sensibility is due to the 

 communication of the nerves with the brain, 

 for any solution of continuity destroys it ; nor 

 can any part be said to be sensible or to possess 

 sensibility which does not communicate with 

 the brain through the nerves. And various 

 parts differ as regards the degree of sensibility 

 which they enjoy, according to the number of 

 nerves distributed to them, and perhaps also 

 according to the manner in which the nerves 

 are connected with them. A touch on the 

 skin covering the olecranon is scarcely felt, 

 whilst the finest point impinging with the 

 slightest force on the skin of the tip of the 

 finger is instantly perceived. 



Sensations differ in kind as well as in degree. 

 The power by which we are made sensible of 

 contact, or by which, under the influence of 

 undue stimulation, we become conscious of 

 pain, is called common sensibility. Doubtless 

 nearly all textures possess this to a certain 

 degree. Tendon and cartilage enjoy a very 

 much less amount of it than skin and muscle. 

 But we can also appreciate the influence of 

 light, of sound, of odor, of flavour, and we 

 art- enabled to do this by means of particular 



