158 



Mr. Graham Brown. 



[Nov. 12, 



may, however, persist for long periods, as long as 20 seconds. The beats may 

 then reappear and again become suppressed, again to appear and persist. 

 The beats at first may be more rapid than before the attainment of main- 

 tained flexion. At first they are synchronous in the two hind limbs, but as 

 they slow in rate of rhythm they again become alternate. 



In records obtained from the individual muscles at the ankle the effects of 

 asphyxia have also been studied (fig. 8). Here the synchronism between the 

 two hind limbs was not investigated, but with this exception the flexor showed 

 the phenomena of asphyxia seen in the case of the intact hind limb. After 

 the commencement of asphyxia there was little or no slowing of the rate of 

 rhythm. The beats at once commenced to increase in height. The maximum 

 was attained just before they began to increase in rate of rhythm. There- 

 after the curve of minimum contraction of the flexor muscle began to rise 

 (that is, the point of minimum contraction occurred at an ever greater level 

 of maintained contraction). At the same time pauses disappeared from 

 between the beats, their rate of rhythm progressively increased, and their 

 extent progressively diminished. Their rate increased from about 1 cycle 

 per second just before asphyxia, to about 3*4 cycles per second just before the 

 complete effect appeared. The beats absolutely disappeared and left behind 

 a state of maintained contraction of the flexor, which gradually increased. 



Recovery from the effects of asphyxia has also been observed in the 

 individual flexor muscle (fig. 8). The state of maintained contraction was then 

 broken by groups of abortive beats which were of very small extent. Soon 

 undoubted beats appeared. These were irregular, of slower rate than before, 

 and of smaller extent. 



The extensor played no part in the phenomena of asphyxia, or of recovery 

 therefrom. Throughout it remained inactive. 



IX. Conclusions. 



That these movements of narcosis progression are strictly equivalent to 

 the normal act of progression there can be no doubt. 



In the rabbit the progression is almost invariably that of hopping — where 

 the two hind limbs move synchronously in the same directions. In the 

 phenomenon of narcosis progression of the rabbit the movements of the two 

 hind limbs are also synchronous. 



In the guinea-pig the progression is almost invariably that of bilateral 

 alternation of movement in the two hind limbs. In the narcosis progression 

 of that animal the movements of the two hind limbs have always been 

 alternate. 



In the cat the movement may either be that of bilateral alternation — as 



