LUDWIG AND MODERN PHYSIOLOGY. y 



secretion of the brain in the same sense that bile is a secretion 

 of the liver or urine that of the kidney ; and many people 

 have imagined this to be the necessary outcome of a too 

 mechanical way of looking at vital phenomena, and that 

 Physiologists, by a habit of adhering strictly to their own 

 method, have failed to see that the organism presents prob- 

 lems to which this method is not applicable, such, e.g., as 

 the origin of the organism itself, or the origin and develop- 

 ment in it of the mental faculty. The answer to this sug- 

 gestion is that these questions are approached by Physio- 

 logists only in so far as they are approachable. We are 

 well aware that our business is with the unknown knowable, 

 not with the transcendental. During the last twenty years 

 there has been a considerable forward movement in Physio- 

 logy in the psychological direction, partly dependent on 

 discoveries as to the localisation of the higher functions of 

 the nervous system, partly on the application of methods of 

 measurement to the concomitant phenomena of psychical 

 processes. And these researches have brought us to the 

 very edge of a region which cannot be explored by our 

 methods — where measurements of time or of space are no 

 longer possible. 



In approaching this limit the Physiologist is liable to fall 

 into two mistakes — on the one hand, that of passing into 

 the transcendental without knowing it ; on the other, that 

 of assuming that what he does not know is not knowledge. 

 The first of these risks seems to me of little moment ; first, 

 because the limits of natural knowledge in the psychological 

 direction have been well defined by the best writers, as, e.g., 

 by du Bois-Reymond in his well-known essay "On the 

 Limits of Natural Knowledge," but chiefly because the in- 

 vestigator who knows what he is about is arrested in limine 

 by the impossibility of applying the experimental method 

 to questions beyond its scope. The other mistake is chiefly 

 fallen into by careless thinkers, who, while they object to 

 the employment of intuition even in regions where intuition 

 is the only method by which anything can be learned, 

 attempt to describe and define mental processes in mechan- 

 ical terms, assigning to these terms meanings which science 



