22 



SCIENCE. 



[N. S. Vol. XV. No. 366. 



To the most important of these environ- 

 mental factors the name 'tropism' has been 

 applied. Heliotropism is the response to 

 light; chemotropism, to chemicals; galvano- 

 tropism, to electricity; stereotropism, to con- 

 tact; geotropism, to gravity; hydrotropism, to 

 moisture; thermotropism, to temperature, etc. 

 All simple instinctive acts are found to be 

 responses to one or more such factors either 

 external or internal; those more complex ac- 

 tions of which nest building and the instinct- 

 ive processes of ants, bees and wasps are rep- 

 resentative are presumably due to a number of 

 factors working simultaneously and giving 

 rise to a series of reflex acts, the whole of 

 which in their interconnection is an instinct- 

 ive action. No one has yet succeeded in 

 satisfactorily analyzing any of these complex 

 activities, but Professor Loeb has confidence 

 that the subjecting of any of them to labora- 

 tory requirements will reveal the same kind 

 of structure as has been discovered in the 

 simple acts. 



The chapter on instinct closes with some 

 remarks concerning the relation of the con- 

 ception presented to ethics. "The analysis of 

 instincts from a purely physiological point of 

 view will ultimately furnish the data for a 

 scientific ethics. Human happiness is based 

 upon the possibility of a natural and harmon- 

 ious satisfaction of the instincts." Such are 

 the significant statements with which we are 

 introduced to the author's ethical philosophy. 

 From the naturalistic point of view ethics can 

 have no other foundation than that indicated 

 above; and there is no doubt that he who is 

 only a physiologist can find complete satis- 

 faction in it. But one feels, instinctively, that 

 Professor Loeb, despite his unpleasant, though 

 appropriate, introductory words concerning 

 the mixing of metaphysical and scientific con- 

 ceptions, is of a philosophic mind, and it 

 seems probable that physiology alone saved 

 him from becoming a technical metaphysician. 



We find upon turning to the discussion of 

 comparative psychology that Professor Loeb 

 considers as the central and chief problem 

 of the physiology of the central nervous sys- 

 tem the study of the 'mechanisms which 

 give rise to the so-called pyschic phenomena.' 



As the elemental psychic fact he names 'as- 

 sociative memory,' by which he means neither 

 more nor less, so far as we can see, than what 

 the psychologist designates as an associative 

 process. Wherever associative memory is 

 found there is material for the psychologist. 

 His first tasli must be to determine in what 

 animals this psychic phenomenon occurs, and 

 his second, to analyze the more complex pro- 

 cesses of higher animals into the elements of 

 the psychic process, much as the instinctive 

 act is analyzed into reflexes. 



An animal which can learn is said to have 

 psychic processes. In this criterion of asso- 

 ciative memory is seen, by Professor Loeb, 

 the basis of a future comparative psychology. 

 Among vertebrates it is well known that as- 

 sociative processes are found; even the Am- 

 phibia and Fishes profit by experience, al- 

 though it is stated by the author that the frog 

 has not yet been proved to have associative 

 mem.ory. Of the invertebrates in this respect 

 little is known for they have not been studied 

 experimentally. But at present it seems safe 

 to say the Coelenterata and Vermes are not 

 known to profit by training. By this criterion 

 of the psychic a very sharp limit for the field 

 of psychology is indicated. Those who do not 

 believe in what Professor Loeb describes as 

 crises in development will not be likely to take 

 much stock in his- conception of the role of 

 comparative psychology until experimentation 

 has proved the abrupt appearance of the as- 

 sociative process in the animal series. For 

 until then there will remain the possibility 

 that the whole thing is a matter of degree of 

 ability to profit by experience, rather than of 

 the presence or absence of a brain mechanism 

 which is able to mediate the association. On 

 this point the author says, "The idea of a 

 steady, continuous development is inconsistent 

 with the general physical qualities of proto- 

 plasm or colloidal material. The colloidal sub- 

 stances in our protoplasm possess critical 

 points." 



Two chapters of great interest treat of the 

 'Cerebral Hemisphere and Associative Mem- 

 ory' and 'Anatomical and Psychic Localiza- 

 tion.' Concerning the valuable experimental 

 data furnished in them we may make only 



