Literary Xoticcs. 367 



changes in afifinity Itetweeii the fil>rillae and fibrillar sul)stance ; they 

 therefore interfere seriously with nervous transmission. The .state of 

 increased sensitiveness to stimuli, whieh is (jne of the first symptoni.s 

 of narcotic action, is due to the destruction of a substance peculiar to 

 the elements of the central nervous system, which normally inhibits 

 reflexes to a certain degree. 



In chajjter 20 it is shown that there are two types of muscle touu:*. 

 The tonus of striated muscle is due to the action of the central nervous 

 system ; in the case of certain non-striated muscles tonus is independ- 

 ent (»f the nervous system, and represents a state of rest. Such muscle 

 passes into a state of tetanus when the central nervous system is re- 

 moved (gastropod mollusks): the nervous system normally inhibits such 

 a condition. 



A brief review of the factors concerned in the inhibition of reflex 

 action (chajjter 21) i^ followed by a descri|Jtion in chapter 22 of the 

 author's important work on the rhythmical contractions of muscle. It is 

 shown that the number of re>piratory movements in fi.«ihes is not regu- 

 lated by the amount of O or C* )., present in the water, but that if the 

 sense organs of the mouth ( avity are jiaralyzed by coeain the move- 

 ments will soon cease completely. The rhythmical muscular contractions 

 during respiration are due to peripheral stimuli, not to a special power 

 with which the muscle is endowed, nor to the influence of the cells of 

 the central nervous system. 



From the j)hvsiological standpoint the vertebrate heart and the 

 bell of the medusa are very similar. If the sinus venosus of the heart, 

 or the sense organs of the nu-dusa are removed, rhythmical contrac- 

 tions cease, but in each case may be niaintained by prolonged artificial 

 stimulation ; the contractions are true reflexes produced by definite 

 stimuli. The transmission of the stimuli from the sinus veno.sus to the 

 ventricle has been assumed to be a jnirely muscular function because 

 the heart of the embryo chick begins to contract before the nervous 

 structures have developed. Kkthe points out that muscle fibers are 

 not yet differentiated at this stage. The weightiest argument against 

 the assumption of nervous transmission in the heart, is the slow rate 

 of conduction (only 30 mm. per second in the frog). But Bkthe 

 shows that the rate of transmission in the dog's heart is about 300 mm. 

 per second: also that if the muscle fibers ot the atrium are renilered 

 functionless by exposure to low temperature, or by the action of mus- 

 karin, stimulation of the atrium will cause contraction of the ventricle, 

 although the muscle fibers of the atrium exhibit not the slightest reaction. 

 It has been observed, too, that the apex oi the ventricle often con- 



