LUDWIG AND MODERN PHYSIOLOGY. 369 



life and organization was supposed to be governed exclusively by its 

 own laws. The work of the past fifty years has been done on the 

 opposite principle, and has brought light and clearness where there 

 was before obscurity and confusion. All this progress we should have 

 to repudiate. But this would not be all. We should have to forego 

 the prospect of future advance. Whereas by holding on our present 

 course, gradually proceeding from the more simple to the more com- 

 plex, from the physical to the vital, we may confidently look forward 

 to extending our knowledge considerably beyond its present limits. 



A no less brilliant writer than the one already referred to, who is 

 also no longer with us, asserted that mind was a 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 

 tliat physiologists, by a habit of adhering strictly to their own method, 

 have failed to see that the organism presents problems to which this 

 method is not applicable, such, e. g., as the origin of the organism 

 itself or the origin and development in it of the mental faculty. The 

 answer to this suggestion is that these questions are approached by 

 physiologists 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 con- 

 siderable forward movement in physiology in the psychological direc- 

 tion, partly dependent on discoveries as to the localization 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 can not be explored by our methods, where measure- 

 ments 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 psy- 

 chological 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 investigator who knows what he is 

 about is arrested in limine by the impossibility of applying the experi- 

 mental 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 mechanical terms, assigning to these terms 

 meanings which science does not recognize, and thus slide into a kind of 

 speculation which is as futile as it is unphilosophical. 

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