Litcrory Xoticcs. 365 



tion of a stimulus to the intestinal wall nf the t'roir will produce con- 

 traction ot" the muscles of the stomach and oesophagus. 



Chapter S gives a detailed account of the staining reacti<tns of the 

 nervous elements. Nissi/s plates and the neurofihrillae owe their pe- 

 culiar staining i)Owers to two sjjeiitlc substances. The "Xissl sub- 

 stance'" is soluble in acjueous solutions of HCl and ammonia ; the 

 "fibrillar substance" is soluble in acid alcohol and many of the ordi- 

 nary fixing reagents. It may be fixed by corrosive sublimate and is 

 insoluble in water, chloroform and ether, (lood ])rei)arations of the 

 fibrillae may therefore be obtained by fixing in ether and substituting 

 ether fur alcohol as a dehydrating reagent. Two methods of this kind 

 are desjcribed. t'entrosomes. intracellular canals, pigmentation, and 

 changes in structure produced by poisons, or due to other abnormal 

 conditions, are ])riefly discussed in chapter 9. 



Nerve degeneration and regeneration form the subiect matter of 

 chapters 10-12. The first evidence of degeneration is the disappear- 

 ance of the fibrillar substance and conse'juent loss of staining power. 

 Degeneration is n(»t necessarily due to the lack of continuity between 

 fi])er and cell but a wound which does not affect the conductibility of 

 the fibrillae may i)ro(luce degenerative changes. The conductibility 

 of fibers may be interrupted by application of pressure or of injurious 

 gases but degeneration will not ensue. The cutting of a peripheral 

 nerve, however, may lead to the degeneration of both the central por- 

 tion of the fiber and its ganglion cell. 



After the lapse of two months or more the normal structure and 

 functional activity of an isolated and degenerate peripheral nerve may 

 be completely restored (auto-regeneration); if severed a second time 

 the distal jtortion only will degenerate ; but if the two ends of such au 

 auto-degenerated nerve are grafted together, a union, both structurally 

 aud functionally perfect, will be established. 



The peripheral nerves of the chick (chaj)ter 13) are formed as 

 chains of cells which may be observed before the processes of the neu- 

 roblasts within the spinal cord have become prominent. These chains of 

 nerve cells differentiate from their substance the axis cylinders, and 

 later become the sheath cells of the fibers. The dendrites of ganglion 

 cells are also developed from a syncytium of nerve cells, and not as 

 outgrowths of single ueuroblasts. 



The nature of nervous transmission is the subject of chapter 14. 

 If by compression, the perifibrillar substance is practically eliminated 

 froiji a certain portion of a fiber without injury to the neurofihrillae, the 

 conductibility of the fiber is not affected. The neurofihrillae must. 



