SOME \E\V BOOKS. 



Introduction to Physiological Psvchologv. By Dr. Theodor Ziehen. 

 Translated by C. C. Van Lieu and Dr. Otto Beyer. 8\ o. Pp. 284. London : 

 Swan Sonnenschein & Co., 1892. 



The original German work, of which this is a translation, forms a 

 useful introduction to the subject. It is short, it is written vivaciously, 

 it is usually clear and well-arranged, always interesting ; it is not 

 a compilation, but the work of a man who has thought out the whole 

 subject for himself. The doctrine is by no means free from exception, 

 but it is set forth vigorously and consistently. In the present state of 

 the subject, any short book is almost necessarily dogmatic in character. 

 Perhaps the few polemical passages were better omitted altogether, 

 as likely to create an unfair impression when not supported by proofs. 



Professor Ziehen belongs to the small but able body of German 

 psychologists who follow the model of the English psychology of 

 association, and seek to improve upon their model. The latter half 

 of the book attempts to show how associative processes account for 

 the complexity of all mental phenomena above sensation. But the 

 chief value of the work lies in the consistent and thoroughgoing 

 attempt to exhibit in detail the physiological processes which underlie 

 the psychical. Without this procedure, hypothetical as it is at present, 

 we are unable to explain mental acts ; and at the same time this 

 method clears up many difficulties, such as those of unconscious 

 mental states. 



Professor Ziehen proceeds upon the hypothesis that ideas are 

 deposited in different elements of the cortex from the corres- 

 ponding sensations, though he is well aware that another hypothesis 

 is possible. Unfortunately, in the very chapter on the association of 

 ideas, his usual clearness deserts him. He does not explain clearly 

 the relation of association by contiguity to association by similarity, 

 and he is confused in dealing with the difficult question of whether 

 the first kind of association is simultaneous or successive. This 

 chapter is one of the less satisfactory parts of the book. His classifica- 

 tion of actions into reflex, automatic (he uses this unhappy word in yet 

 another sense) and actions proper, is well worked out, but it presents 

 many difficulties. He has to class instincts along with reflex and auto- 

 matic acts (/.£., reflexes modified by intercurrent sensations — why sensa- 

 tions ?) as purely unconscious. The first half of the book is an 

 account of the various sensations, and of generalisations, like 

 those of the speciiic energy of nerves and of Weber's law. A fuller 

 account of colour-blindness and of Hering's liypothesis would be an 

 advantage. The psychophysical methods are treated very inade- 

 quately, even making allowance for the difficulty of discussing them in 

 a short book ; and the treatment of the method of right and wrong cases 

 (which the translators, following Professor Ladd, absurdly call the 

 method of correct and false (mistaken) cases) is apt to be misleading. 

 Still, on the whole, the selection made from the multitude of data 

 is a good one for elementary purposes, and the statement is clear, 



