48 



SCIENCE. 



[Vol. X. No. 250 



BOOK-REVIEWS. 



The American Journal of Psychology. Ed. lay G. Stanley 

 Hall. Baltimore. 



The announcement made some months ago, that a journal de- 

 voted to the scientific aspects of psychology was to be published 

 under the auspices of the Johns Hopkins University, excited con- 

 siderable comment. Some seemed to think that we had philosophi- 

 cal journals in abundance, and whatever surplus energy America had 

 in reserve in this direction might well be utilized in strengthening 

 the journals of England and the continent ; others doubted whether 

 so small a department could really supply material enough to sus- 

 tain even a quarterly periodical ; while those who have not yet be- 

 come acclimatized to the new atmosphere that is slpwly but surely 

 displacing the old, dogmatic, non-progressive, and lifeless treatment 

 of psychological topics, intimated that they saw in the new-comer a 

 further belittling of a noble study, and the harbinger of a much hated 

 ' materialism.' The first number of the journal proves beyond a 

 doubt, that, for a time at least, the material will not be wanting, 

 and quite as certainly shows that the movement in favor of an ex- 

 perimental psychology is strong and important enough to merit a 

 separate organ of publication. If we add to this the guaranty of 

 sound scholarship and all-sided appreciativeness that the name of 

 the editor (as also of the university from which it comes) affords, 

 we seem justified in welcoming the journal as an ornament to 

 American science, and as promising to mark an era in the develop- 

 ment of one of the most significant movements of our age. 



The two main purposes of the journal are to publish original 

 studies, and to review the psychological literature. The first is 

 represented by four articles, all worked out upon an experimental 

 basis ; while the critiques and notices fill no less than seventy-eight 

 finely (perhaps too finely) printed pages. The leading article is con- 

 tributed by Dr. Warren P. Lombard, and describes a very remark- 

 able series of experiments upon the variations in the extent of the 

 ' knee-jerk ' under various conditions of the nervous system. It is well 

 known that if one leg is supported, and the knee partly flexed (most 

 conveniently by crossing one leg over the other), a sudden blow 

 upon the ligament just below the knee-pan will cause an involun- 

 tary and jerky movement of the foot. This apparently insignifi- 

 cant phenomenon became of special importance when it was ob- 

 served that it was generally absent in a common form of spinal-cord 

 affection known as Tabes dorsalis. The nature of the process is 

 discussed in quite an extensive literature, and the two main opinions 

 regard it as (i) a simple reflex act, with a direct course from the 

 tendon to the lumbar cord and back to the muscle, and (2) as an 

 act not reflex (because the time it takes is much too short), but 

 rather as a mechanical effect under the influence of a reflex centre, 

 — a 'tone' rendering the muscle more or less susceptible to such 

 stimuli. In either case the variations in the extent of the move- 

 ment are co-ordinated with the condition of the nervous centres, 

 and thus become an index — and, as Dr. Lombard shows, an in- 

 credibly delicate index — of a very mysterious central process. 

 Previous observers had shown that a violent contraction, such as 

 clinching the hands, or even slighter movements, as well as strong 

 sensory stimuli, just before the striking of the ligament, greatly 

 increased the e,xtent of the resulting movement. This was ex- 

 plained by supposing that the effect of the movement was to in- 

 crease the irritability of the cord-centres (perhaps by removal of 

 inhibitory influence from the brain), on whose integrity the knee- 

 jerk depends. Dr. Lombard was able to secure more delicate re- 

 sults by substituting a blow from a hammer swinging through a 

 definite arc, and striking with a constant force for the unequal 

 movement of the hand, and the writing of the resulting movement 

 of the foot on smoked paper instead of its rough estimation by the 

 eye. The first result of this method was to show that the extent 

 of successive knee-jerks produced by equal blows of the hammer 

 was very different ; and this, too, when the subject was lying per- 

 fectly at ease, and so avoided all re-enforcements by voluntary mo- 

 tion. On comparing these variations with those resulting from true 

 re-enforcements, it was clear that they might be due to very slight 

 changes in the individual ; and, by taking the average of a score of 

 movements, it was found that their extent varied quite constantly 

 with the force of the blow. 



Dr. Lombard then subjected himself for two weeks to a tedious 

 routine of work, recording his knee-jerk under precise conditions at 

 eight definite times of the day, and keeping a diary of his general 

 condition, as well as recording the condition of the temperature, 

 barometer, etc. In this way he accumulated the records of over six 

 thousand observations, suggesting several interesting results. In 

 brief, he shows that this index of the condition of the nervous sys- 

 tem is sufficiently delicate to be regularly influenced by the time of 

 day (it begins low, rises very much after breakfast, and then grad- 

 ually sinks with several ups and downs) ; by the taking of a meal 

 (notably rising after breakfast) ; by fatigue, either physical or mental 

 (in both cases showing marked decrease) ; by the slightest movement 

 (i.e., the re-enforcements by talking, swallowing, etc.) or attractive 

 sensations of sound, light, etc.; by all kinds of mental excitement ; 

 by holding the breath (a very marked increase when held for a 

 minute or so) ; by the state of the thermometer (in general dimin- 

 ishing as the temperature increases), as of the barometer (quite 

 closely rising and falling with a rise and fall in the barometric 

 column). 



An adequate idea of the delicacy of these variations with different 

 mental conditions can only be gained by a citation. " One day 

 during the experiments a procession passed the end of the street, a 

 short distance away, and the effect of the music was very evident. 

 The twenty-five experiments of the examination which had just 

 been made had shown the average knee-jerk to be 32 millimetres. 

 At the approach of the procession, the subject resumed his place on 

 the apparatus, but the first blow was not struck until the first band 

 was passing the end of the street, — 60,' 71, 74, 70, 60, 55 ; another 

 band immediately followed, and it began to play 'My Maryland' 

 just before it reached the street, — 62, 76, 76, 74, 71, 66, 59, 64, 59; 

 this was followed by a drum corps, — 48, 55, 51, 55, 53,49, 52 ; and 

 then the music died away in the distance, and only the ordinary 

 street-sounds remained. — 40, 45, 37, 30, 39, 53, 37, 29." In short, 

 not only does music re-enforce the knee-jerk, but the character of 

 the music, especially its emotional power, determines the amount of 

 such influence. That these results are not the result of an anticipa- 

 tion by a theory is shown very conclusively by the fact that on 

 several occasions Dr. Lombard fell into a more or less deep sleep 

 during the experiments, and, if the blow happened to come just 

 after dreaming of an exciting event, the knee-jerk (very low by the 

 inactive condition of the subject) showed a sudden rise. The phe- 

 nomena are thus taken outside the conscious realm. It seems no 

 illegitimate use of the imagination to picture the time when the 

 inquiry after one's health will take the form of, " How is your knee- 

 jerk? "or the poet describing the effect of anger will exclaim, 

 " Truly, my knee-jerk arose." 



The remaining articles — on dermal sensitiveness to gradual 

 pressure-changes, by Prof. G. Stanley Hall and Yuzero Motora ; on 

 a method for the experimental determination of the horopter, by 

 Christine Ladd-Franklin ; and on the psychophysic law and star- 

 magnitudes, by Dr. Joseph Jastrow — are of a more technical 

 character ; and this is a very laudable feature, for it serves not only 

 to frighten off the many dilettanti of psychic research, but to justify 

 the strictly scientific methods of psychology. Professor Hall and 

 Mr. Motora describe a new method of experimentation, by which a 

 weight pressing upon the finger is either gradually increased or 

 gradually diminished, and the sensibility is measured by the time 

 necessary for the subject to decide in which direction the change 

 has been made. The problem is a very complex one, involving not 

 only the amount of change, the rapidity of change, and the initial 

 pressure, but also the ' confidence ' of the subject. The interesting 

 results reached are only preliminary, but foretell a hopeful future 

 for this valuable new method. Mrs. Franklin describes a very 

 striking illusion, consisting of the appearance of a third line at right 

 angles to the plane of the paper, on which a pair of crossed lines, 

 with their acute angle towards the observer, are viewed in a certain 

 position relative to the eyes. These small upright phantom-lines 

 are so distinct that they furnish a means of determining the shape 

 of the horopter (i.e., the sum of the points which in a given position 

 of the eyes will seem single), at least in its simpler forms. Dr. 

 Jastrow utilizes the comparison of the photometrically measured il- 

 luminating powers of the stars (made by the Harvard Observatory) 



^ The numbers refer to the extent of the knee-jerk in millimetres 



