EXCITATION AND TRANSMISSION 69 



possible, but it may be pointed out that even in such 

 tissue a transmission decrement may occur, if the trans- 

 mission path is of such a kind that the maximal excita- 

 tion decreases along it. Certain kinds of muscle tissue 

 and medullated nerve have been found to react according 

 to the "all-or-none" law, although even the medullated 

 nerve, the most highly specialized of conducting tissues, 

 shows a decrement when cooled, partially asphyxiated 

 or partially anesthetized. 1 But we are concerned rather 

 with general protoplasmic excitation and transmission 

 than with the highly specialized conductive processes, 

 and concerning the existence, at least very generally, 

 of a decrement in such transmission there seems to be 

 no doubt. 



When a region of relatively high activity or of excita- 

 tion is established by the action of an external factor 

 in a protoplasm which is not specialized with reference 

 to transmission, transmission from this region must 

 occur to some extent, and from our knowledge of pro- 

 toplasmic transmission in general we must expect that 

 a decrement in intensity or in effectiveness of the trans- 

 mitted change will occur. In other words, excitation 

 and transmission in protoplasm in general usually give 

 rise to an excitation gradient. The evidence at hand 

 concerning the existence and origin of the axial gradients 



'As regards nervous conduction see Biedermann (1903 and refer- 

 ences), Boruttau (1901), Ducccschi (1901), Fischer (191 1), Lodholz 

 (1913), Lucas (191 7, particularly chaps, ii-v and references). The 

 question of the normal occurrence of a decrement in certain regions of 

 the nervous system is also considered by Lucas. Tashiro has observed 

 a gradient in CO* production in certain nerves, the rate decreasing in 

 the direction of functional conduction (Tashiro, 1914, 1015a. b, 1917, 

 particularly chap. iv). I have found that susceptibility in certain 

 nerves decreases in the dire tion of functional conduction (Child, [914a). 



