628 METABOLISM IN NERVES. 



is quickly changed to an acid reaction after death (?by fermentation lactic acid). 

 The reaction of the nerve-fibers during life is variable. After the ingestion of 

 methylene-blue Ehrlich found in living animals that the substance of the axis- 

 cylinders stains blue, especially in those nerves that yield an alkaline reaction 

 (cerebral cortex, cardiac nerves, the sensory and motor fibers of the unstriped 

 muscles, gustatory and olfactory nerve-endings) , while the endings of the voluntary 

 motor nerves, which he considers have an acid reaction, remain unstained. Ac- 

 cording to Flesch the ganglion-cells exhibit differences in their reactions to stains, 

 in accordance with their functions. The irritated nerve develops carbon dioxid. 



As dead nerves exhibit increased consistence, it is probable that a 

 condition of rigidity develops in them after death comparable to mus- 

 cular rigidity and attended with the development of free acid. Fresh 

 brain rapidly scalded at 100 C. remains alkaline (as do the muscles). 



The gray matter contains more water (from 83 to 84 per cent.) than the 

 white (from 68 to 70 per cent.). The dried material contains albumin (in the 

 gray matter 30.89 per cent., without nuclein), partly soluble, partly insoluble 

 (in the white matter 19.33 per cent., without nuclein and neurokeratin) ; lecithin 

 17.2 per cent. (9.9 per cent.); cholesterin and fats 18.7 per cent. (51.9 per cent.); 

 cerebrin 0.5 per cent. (9.5 per cent.); extracts insoluble in ether 6.7 per cent. 

 (3.3 percent.); salts 1.5 per cent. (0.6 per cent.); the gray matter contains 

 more phosphoric acid; neurokeratin (0.3 per cent, in moist peripheral nerves, 

 2.9 per cent, in moist white brain-matter). Breed found in 100 parts of ash: 

 potassium 32, sodium n, magnesium 2, calcium 0.7, sodium chlorid 5, iron phos- 

 phate 1.2, combined phosphoric acid 39, sulphuric acid o.i, silicic acid 0.4. 



Among the mechanical properties of nerve-fibers the absence of elastic tension 

 in the various positions of the body is noteworthy. This is recognized from the 

 fact that divided nerves do not retract and that the nerve breaks up on its surface 

 into delicate macroscopically visible transverse folds (Fontana's transverse stria- 

 tion) . 



The marked cohesive resistance of the nerves to traction is responsible for 

 the fact that when a part of the body is forcibly torn from the trunk, as in machin- 

 ery accidents, the nerve-trunks often resist. The nerve, however, readily breaks 

 up into its individual fibers. 



If a constant electrical current be passed through an excised (or even dead) 

 nerve there is a motor reaction of the contents of the fibers to the anode, of the 

 sheath to the kathode. 



METABOLISM IN NERVES. 



Little is at present known concerning metabolism in nerves. The 

 occurrence of various extractives has been determined, and these must be 

 considered as decomposition -products. On the other hand, it has not 

 yet been possible to demonstrate with certainty an interchange of oxygen 

 and carbon dioxid. That, however, anabolism from the blood must take 

 place in the nervous tissue is indicated by the fact that the irritability 

 of the nerves diminishes after compression of the blood-vessels, and 

 returns on restoration of the circulation. Thus, compression of the 

 abdominal aorta is followed by paralysis of motion and sensation in 

 the lower half of the body; occlusion of the cerebral vessels gives rise 

 to almost immediate abolition of the functions of the cerebrum. Under 

 such Circumstances, the poverty of the nerve-trunks in blood-vessels is 

 striking. As, however, the central nervous organs, especially the brain, 

 undoubtedly receive a larger blood-supply the opinion seems justified 

 that they are the seat of more active metabolism than the simple 

 conducting apparatus. The ganglia form much lymph. 



Hodge, Vas, Nissl, Mann, Beek, F. Pick, and others have studied the changes 

 in the ganglion-cells that take place as a result of activity and exhaustion. It 



