Literary Notices. 



clxxxvii 



J3l 



of stimulus = D ; discrimination threshold = S ; threshold of stimu- 

 lus = German S ; [or we may substitute Si.] A stimulus used as a 

 constant for reference is N, while another to be compared with it is 

 V. mV is the mean variation derived from division of a series of 

 observed errors by the number of observations. The less mV the 

 finer the sensation and discrimination. Since relative and not abso- 



m V n „ m V 



lute errors are most important ~r~ ~TT are used. 



The sections devoted to the methods of gradual variation (Ab- 

 stufungsmethoden) and error methods are full and clear enough for 

 the student. For example, the method by minimal variation is thus 

 illustrated. 



Upon the vertical A B the amounts of the stim- 

 uli are indicated from sub-observable (A) to super- 



V 



observable (B). Beginning at r, r is varied till a 

 judgment is reached that a sensation is present. 

 This value Si o is noted on the diagram and the 

 change continued until a decided sensation is reach- 



A 



ed, r. Now the stimuli are varied in the opposite 

 direction until the subject decides that the sensa- 

 tion has ceased. This value Si u is recorded and 



Sl ° + Sl u = Si , or the threshold of stimulus. In 



a similar way the method of equivalence, method of 

 minimal variation, method of super-perceptible dif- 

 are treated. The mathematical technicalities of the 

 methods by error are briefly disposed of and stimulus and nerve ex- 

 citement are taken up. The doctrine of specific energy of nerves is 

 dismissed at once. No description of the anatomical and physiolog- 

 ical elements of the nervous system is attempted. The theory of 

 nervous translation, so dear to a Wundtian heart, accordingly does not 

 appear. The discussion is but moderately well carried out. 



The section on pressure sense shows a discriminating use of the 

 recent papers of Dessoir, Goldscheider, Blix and others while it is not 

 burdened with references or conflicting views. The vast system of 

 subordinate qualities often built up upon the pressure sense is swept 

 away and tickling, tactile sensnsations, pain and the like are all refer- 

 red to complexes of qualities. Pain is not a special quality of the skin 

 sense but a feeling which may result from the excitation of any sensory 

 nerve. No reference is made to the theory which daily becomes 



