1912.] 



" Narcosis Progression " in Mammals. 



161 



There is no space here to discuss all the points of interest raised by these 

 phenomena, but I should like to mention one. The rhythmic act of pro- 

 gression resembles that of respiration in so complete a degree that it is 

 difficult, if not impossible, to resist the idea that in all essentials they are 

 the same, and conditioned in similar manners by similar mechanisms and 

 by stimuli of similar sources. 



There is a phenomenon of " voluntary breathing " just as there is one of 

 " voluntary progression." But the former act tends soon to become 

 involuntary ; and although progression seems to be more under the 

 influence of the higher centres, yet it, too, tends to become an involuntary 

 act once started. The rhythmic movements of respiration seem essentially 

 to be central ; they appear to continue after the abolition of self- 

 engendered impulses. In a similar manner it appears that the movements 

 of progression in the lumbar centres may appear when self-generated 

 proprioceptive impulses are excluded. Yet both respiration and progression 

 are reinforced by a peripheral self-regulative mechanism. The effects of 

 asphyxia upon the two centres are again very similar ; for in its effects 

 upon the respiratory centre it first produces an increase in the amplitude 

 of the respiratory movements. A state of maintained inspiration underlies 

 this, the diaphragm may continue contracted to a certain extent even at 

 the end of expiration. With an increase of the expiratory movements the 

 inspiratory movements become small. 



It looks as if there were here, and up to this stage in the asphyxia 

 phenomena of respiration, a resemblance between the behaviour of the 

 inspiratory centre and the flexor centre in progression. Is it possible that 

 the flexor centre is strictly comparable to the inspiratory centre ? That 

 flexion = inspiration, and extension = expiration ? 



In the case of progression it is again of interest that asphyxia should 

 produce an increase in extent and rate of rhythm of the movements. The 

 act of progression if of sufficient speed itself may cause a certain degree 

 of asphyxia. If this be not too great it will assist rapid movement through 

 the environment. When carried to too great an extent the movements 

 will be retarded, and the state of asphyxia will therefore be lessened. 

 There is thus here possible a nice internal regulation of the speed of 

 progression, and an optimum speed may be set for each resultant of the 

 balance between the local peripheral and central factors, and the higher 

 central and peripheral factors, which all influence the final centres which 

 condition the act. 



