174 TRANSACTIONS AND PROCEEDINGS OF THE [Sess, Lxvi. 



katabolic inertia. An active state has been set up in an 

 end-organ, and has thence been propagated into the central 

 nervous system ; a particular sensation is the conscious 

 counterpart. The stimulus is now suddenly withdrawn, 

 but, as is well known, the sensation does not equally 

 suddenly cease — it persists as the + after-sensation due to 

 the katabolic inertia of the tissues involved. This is well- 

 marked in the case of sight, where the + after-image is the 

 correlative in consciousness of the continued activity (post- 

 stimulant) of the retino-cerebral protoplasm, i.e. its katabolic 

 inertia. It is to this inertia that the beautiful modern 

 illusions of seeing movement are due, in the instruments 

 known as kinematograph (kinetoscope, mutoscope, etc.). 



II. The functional inertia of resting protoplasm, i.e. of 

 the characteristically anabolic phase (anabolic inertia) is 

 quite as well marked, though there may not be so many 

 familiar examples. We have just spoken of the -1- after- 

 image ; we have a good example of anabolic inertia in the 

 negative after-image. After retinal activity — the katabolic 

 phase — has existed for some time, the phase of relative 

 rest, reconstruction must supervene, and this gives in con- 

 sciousness the — after-image (reversal of black and white, 

 complementary colours, etc.). Now very often this fades 

 away and is succeeded by the -f- after-image, that again 

 by the — , there being a series of alternating metabolic 

 phases — the rhythmical or oscillatory expression of the 

 retinal functional inertia, the analogue in living matter of 

 the to and fro swing of the pendulum or the vibrations of 

 the jelly. 



Anabolic inertia is well expressed in terms of time- 

 delay, by the familiar " true latent period " of the 

 stimulation of muscle. The muscle is at rest or in its 

 anabolic phase, and the functional inertia of this is ex- 

 hibited in the no doubt short, but demonstrable, interval 

 between the reception of the stimulus and the commence- 

 ment of response. In striated muscle it is very short (less 

 than T^")' ii^ nonstriated it is much longer, -5 " ; in other 

 w^ords, nonstriated muscle has greater anabolic inertia than 

 striated, and this agrees precisely with the conception of 

 functional inertia being the counterpart of irritability, 

 for nonstriated muscle has less irritability than striated. 



