CHAP, v.] NUTRITION. 869 



disruptive processes checked, whereby the setting free of energy 

 is checked and so the beats hindered or stopped, the immediate 

 inhibitory effect being followed by a period of rebound in which 

 the savings of the inhibited period are spent in increased action. 

 Conversely the cardiac augmentor impulses appear to assist the 

 katabolic and to hinder the anabolic changes, and hence when they 

 have done their work leave the tissue with diminished capital 

 manifested by feebler beats or by the absence of the power to 

 beat. In other instances of inhibitory action, such as that of the 

 respiratory centre, there seems to be an increase of anabolic 

 events ; and we may perhaps say that in general inhibition is 

 accompanied by a prominence of anabolic changes. But we must 

 not infer that an increase of anabolic changes always means in- 

 hibition. On the contrary, when we have to study the origination 

 of visual impulses in the retina we shall come upon a view that a 

 wave of light may affect what we shall call a visual substance 

 either by promoting anabolic constructive changes or by in- 

 creasing katabolic destructive changes according to its wave 

 length ; but in each case the effect is a positive one, that is to 

 say, the light gives rise to sensation, the difference between the 

 two cases being only a difference in the kind of sensation. 



549. One value perhaps of such a view lies in the fact that 

 it warns us against assuming that a nervous impulse can only 

 produce disruptive katabolic changes such as are seen in muscular 

 contraction or in secretion. The effects of stimulating a nerve 

 going to a muscle or a salivary gland are striking and obvious, and 

 the behaviour of a muscle or a gland so far as contraction and 

 secretion are concerned is, within certain limits, under experimental 

 control. But there are certain phenomena, seen chiefly in the course 

 of disease, and lying, to a very small extent only, within the control 

 of experiment, which seem to shew that the central nervous system 

 governs the metabolic changes, the nutrition, not only of muscle and 

 gland, but of various other tissues in a deeper and more general 

 way than that of simply promoting (or hindering) contraction or 

 secretion. Thus as we have seen ( 83) when the connection 

 between a muscle and the central nervous system is severed, the 

 muscle eventually wastes and loses its vitality. When all the 

 nerves going to the sub-maxillary gland are severed, the gland 

 instead of being as in the normal condition intermittently active 

 and quiescent, pours forth a continuous " paralytic " secretion and 

 eventually degenerates and wastes. When in a rabbit the fifth 

 nerve is divided in the skull the loss of sensation in those parts of 

 the face of which it is the sensory nerve is followed by nutritive 

 changes. Very soon, within twenty-four hours, the cornea becomes 

 cloudy ; and this is the precursor of an inflammation which may 

 involve the whole eye and end in its total disorganization. At 

 the same time the nasal chambers of the side operated on are 

 inflamed, and very frequently ulcers make their appearance on the 



