May 21, 1909] 



SCIENCE 



803 



great or when it is too slow continued 

 metabolism, or life, may be endangered. 

 The tempo is altered when it becomes neces- 

 sary for the living matter to do work. 

 More energy must be absorbed, the greater 

 the work done, and this needed increase in 

 energy can be secured only by increasing 

 the speed with which the metabolic process 

 takes place. 



I wish to caU attention to the fact that 

 in even the simplest unicellular organism 

 its normal processes are purposeful. The 

 cell molecules attract substances that serve 

 them best as foods. From these they select 

 the parts that they can utilize, and reject 

 the parts that can not serve them. This is 

 true, however, only within certain limits, 

 because often they do absorb substances 

 that lead to their own destruction. Their 

 selection seems to be guided by chemism, 

 which on the whole leads them in the safe 

 way, but may cause their destruction. 



It is not my purpose to discuss at this 

 time the question of the relation between 

 the existence of a nervous system and con- 

 scious action or psychical activity, but I do 

 wish to call attention to the fact that low 

 forms of life in which there is no trace of 

 nerve tissue behave in a purposeful man- 

 ner. Many of the low forms of life in 

 which there is no trace of the development 

 of the sense of sight, or sound or feeling, 

 are responsive to light, to sound and to 

 stimulation. We see most convincing evi- 

 dence of this in the phenomena of helio-, 

 thermo-, ehemio- and galvano-tropism. 

 Under the influence of optical, thermic, 

 chemic and electric stimuli these low forms 

 of life, devoid of any trace of nervous sys- 

 tem, manifest movements that serve them 

 in self -protection, in securing food and in 

 reproduction. These lower forms of life 

 without nerve tissue apparently learn by 

 experience to choose between what is good 

 and what is bad for them. Metalnikov 



placed carmin in a fluid in which ciliated 

 infusoria were swimming. At first they 

 absorbed the carmin granules, but having 

 done so once, they could not be induced to 

 try this food again. This behavior, it must 

 be admitted, is much the same as that of 

 the dog which, having been struck with a 

 stick once, runs away when he again meets 

 the same man with a stick. Certain in- 

 fusoria that feed v^on bacteria select the 

 species upon which they feed. The move- 

 ments of infusoria in pursuit of their prey 

 are certainly purposeful, if not conscious. 

 The readiness with which low forms of life 

 accommodate themselves to altered environ- 

 ment shows that they are capable of being 

 trained or educated to a certain extent. 

 Stahl has shown that a certain Plasmodium 

 flees when sprinkled with salt, but if the 

 salt be added to the medium gradually the 

 organism accommodates itself to the new 

 medium. Purposeful action is manifested 

 by plants as well as by animals, and by 

 both unicellular and multicellular plants. 

 This is in evidence in the movements of 

 algae and moulds. Leaves turn toward the 

 sources of light and heat, and the roots seek 

 nourishment in the earth. The capability 

 of responding to certain stimuli is common 

 to all cell life, whether it be vegetable or 

 animal. 



In multicellular animals, such as man, 

 we have colonies, or groups of cells, or 

 organs, bound together. Each kind of cell 

 has its own peculiar molecular composition 

 and through these living molecules the 

 work of the organ is accomplished. A 

 framework of bone, cartilage and connect- 

 ive tissue support and hold in position 

 these organs. They are supplied with food 

 material by a common system of blood and 

 lymph vessels, and their harmonious action 

 is secured through the nervous system. 

 The digestive organs roughly prepare the 

 food for all, but each has its own secretion 



