230 UNIVERSITY OF COLORADO STUDIES 



of the emotions, yet it cannot be said that expression is any evidence of 

 consciousness. Expression may be entirely instinctive, or more cor- 

 rectly tropic. Goltz showed that a dog after having its cerebral hemi- 

 spheres removed would still growl and snap if teased, and this creature 

 certainly had no consciousness. 1 This fact is thoroughly understood 

 by physiologists and is supported by many experiments on cerebral 

 extirpation. 2 



Nothing originates all at once like a creation by fiat but all things 

 are in a state of continuous growth and development. Not only are 

 tropisms necessary predecessors of consciousness, but so also is a ner- 

 vous system. An idea of the development of a nervous system in lower 

 organisms will help us to understand it in higher forms. The entrance 

 of a nerve element into a mass of tropic plasma must have proven an 

 advantage to both elements vouchsafing their survival. 



From the standpoint of evolution any organism might be regarded 

 as a community of cells each of which performs a function for the whole 

 group. Thus through the economy of the division of labor, and speci- 

 alization, the group organism, in competition with other cells and 

 groups, in the struggle for existence, is rendered more efficient, and 

 consequently is able to survive. In this division of labor in the group 

 organism the nerves prevent the response impulses from being diffused 

 throughout the mass but transmit them by natural selection to the 

 place where the response yields the most efficiency to the organism. 

 These nerve elements guarantee greater effectiveness and sensitiveness. 

 Loeb 3 has shown that a stimulus is about eight times as effective in 

 the normal ascidians than it is when the nerve ganglia are removed. 

 If the efficiency of the response, and hence the animal's efficiency for 

 life is conditioned by the increase of nerves, and assuming that nerve 

 supply varies in the organism (as it certainly does), then natural selec- 

 tion will favor increase of nerve supply. This multiplication of nervous 

 substance ultimately gives rise to the association memory and con- 

 sciousness. 



1 Der Hund ohne Grosshirn, Pfliiger's Archiv., Bd. 51. 



2 Exner, Entwurj zu einer physiologischett Erklarung der psychischen Erscheinungen. Leipsig, 1894; 

 Schrader, "Zur Physiologie des Vogelgehims," Pfiitger's Archiv., Bd. 44. Loeb, Physiology of the Brain, 

 1900, pp. 268, and 275. 



■s Physiol, oj the Brain, p. 38. 



