818 



SCIENCE. 



[N. S. Vol. VII. No. 181, 



the medulated fibre which preserves its 

 sheath up to the point where its large nu- 

 cleus appears. The latter occupies the lu- 

 men and is quite conspicuous, while ectad 

 of it the fibre is reduced to a sensory rod 

 with small rigid styles or cilia at the apex. 

 Such termini are quite generally distributed 

 over the skin of the head and take the place 

 of the buds found in other types. The 

 double staining is exceptionally good, and 

 teased preparations produced by pressure 

 on the cover glass permit the isolation of 

 the termini and their study under immersion 

 lenses. It seems probable that the differ- 

 ences of opinion which still prevail in this 

 matter are the result of the partial results of 

 the different methods, and that the truth 

 will be reached by an intelligent employ- 

 ment of the data from them all. In con- 

 clusion the writer desires to acknowldgee 

 the substantial assistance rendered, espe- 

 cially in the laboratory manipulation on 

 which this paper is based, by his friend Mr. 

 G. E. Coghill, in collaboration with whom 

 a more detailed report of the histological 

 processes and results may be expected in 

 the Journal of Comparative Neurology at no 

 distant date. 



C. L. Hebrick. 

 Univeesity of New Mexico. 



SOME EXPERIMENTS ON ANIMAL INTELLI- 

 GENCE. 



The results of a recent investigation on 

 animal intelligence, the details of which are 

 about to be published, =i= seem to be of sufiB- 

 cient general interest to deserve an inde- 

 pendent statement here. The experiments 

 were upon the intelligent acts and habits of 

 a considerable number of dogs, cats and 

 chicks. The method was to put the animals 

 when hungry in enclosures from which they 

 could escape (and so obtain food) by oper- 



* Animal Intelligence ; An Experimental Stndy of 

 the Associative Processes in Animals ; Psychological 

 Peview, Supplement No. 8. 



ating some simple mechanism, e. g., by turn- 

 ing a wooden button that held the door, pull- 

 ing a loop attached to the bolt, or pressing 

 down a lever. Thus one readily sees what 

 sort of things the animals can learn to do 

 and just how they learn to do them. Not 

 only were the actions of the animals in 

 eifecting escape observed, but also in every 

 case an accurate record was kept of the 

 times taken to escape in the successive 

 trials. The first time that a cat is put into 

 such an enclosure, some minutes generally 

 ■elapse before its instinctive struggles hit 

 upon the proper movement, while after 

 enough trials it will make the right move- 

 ment immediately upon being put in the 

 box. The time records show exactly the 

 method and rate of progress from the former 

 to the latter condition of affairs. A graphic 

 representation of the history of six kittens 

 that learned to get out of a box 20 x 15 x 12 

 inches, the door of which opened when a 

 wooden button 3J inches long, f inch wide, 

 was turned, is found in the curves in Figure 

 1. These curves are formed by joining the 

 tops of perpendiculars erected along the 

 abscissa at intervals of 1 mm. Each per- 

 pendicular represents one trial in the box ; 

 its height represents the time taken by the 

 animal to escape, every 1 mm. equalling 

 10 seconds. A break in the curve means 

 that in the trials it stands for, the animal 

 failed in ten minutes to escape. Short per- 

 pendiculars below the abscissa mark inter- 

 vals of twenty-four hours between trials. 

 Longer intervals are designated by figures 

 for the number of days or hours. The 

 small curves at the right of the main ones 

 are, as the figures beneath them show, 

 records of the skill of the animal after a 

 very long interval without practice. This 

 process of associating a certain act with a 

 certain situation is the type of all the intelli- 

 gent performances of animals, and by thus 

 recording the progress of a lot of animals, 

 each in forming a lot of each kind of associa- 



