in LIVING MATTER 85 



exclusively morphological and are treated at length in text-books 

 of histology, to which the reader should refer. 



Very undetermined also, and far from concrete, is our know- 

 ledge of the internal conditions and stimuli of all those vital acts 

 of which protoplasm is capable, even when it is as far as possible 

 protected from every external agent that can function as a 

 stimulus, by deviating from the general external conditions. 



Some hold that the stimulus to movement and other auto- 

 matic acts arises in the waste products that develop and accumu- 

 late in the cell, in consequence of its metabolism. In this case 

 it is evident that both automatic excitations and reflexes are 

 the effect of stimuli extrinsic to the protoplasm ; but in the former 

 these are generated by the activity of the organism itself, in the 

 latter they come from without. 



The intrinsic fallacy of this doctrine is easily appreciated when 

 we consider that, on its showing, all the phenomena of excitation, 

 paralysis, or of fatigue that are seen in the different forms of auto- 

 intoxication must be regarded as automatic phenomena, because 

 the agents by which they are determined (e.g. carbonic acid, 

 as in asphyxia from suffocation, urinary products, as in uraemia, 

 muscular toxins, as in fatigue or exhaustion consequent on exces- 

 sive and prolonged muscular exertion) all originate in the meta- 

 bolic activity of the different tissues of the body. 



The true concept of automaticity is very different : either we 

 must demonstrate that there are no automatic phenomena, properly 

 speaking, or we must hold that the stimulus, or, more generically, 

 the determining cause of the phenomena, is intrinsic to the 

 elementary organism which exhibits them, and consists in an oscil- 

 lation (rhythmical or irregular) of its metabolism or its excitability, 

 by which it finds within itself the conditions for the development 

 of the energy it has stored up (Luciani, 1873). The chemical and 

 molecular transmutations of protoplasmic metabolism are usually 

 conceived as something continuous and monotonous, which can 

 only be changed or modified by external influences ; but nothing 

 forbids us to imagine a more vital process, which without invoking 

 external factors may become disturbed of itself, or in consequence 

 of the particular structure of the protoplasm, or the facility with 

 which the particles of which it is composed are able to change their 

 relations. 



XIV. Various hypotheses and theories have been put forward 

 as to the nature of the intimate processes that go 011 in living 

 matter, and by which the several vital phenomena, thus briefly 

 summarised, are determined. The starting-point and fundamental 

 concept from which these different speculations have for the most 

 part been evolved is invariably the same, starting from the oft- 

 accentuated hypothesis that chemical energy is to be regarded as 

 the sole and ultimate cause of all the manifestations exhibited by 



