666 THE HIGHER ANTHROPOIDS 



environment mow extensively, for ereating new modes of action, for augment- 

 ing the stream of sensory impressions from contacts lieretolore unknown — 

 in a word, for the discovery and control ol new territories in tlie reahn of 

 behavior. How much more the hand actLially means to the goriHa than to 

 any of the lower primates may be inferred from the history of John Daniel 

 who, in many particulars, approached the human standards ol manual manip- 

 ulation. In the acquisition of these manipulations, as well as m their execu- 

 tion, a harmonious interaction is necessary between the muscles of the 

 eyeballs, of the neck moving the head in the various directions, of the forearms, 

 arms and hands in order that the object of these movements may be attained. 

 The structural expansion of the inferior olivary nucleus accords closely 

 with the increment in function witnessed in the increased capacity of the 

 gorilla for the simultaneous regulation of eyes, head and hand. The evolu- 

 tional unfolding of the inferior oli\ary body is one of the most striking 

 features in the brain stem of the primates. 



The features of the brain stem selected for comparative study of their 

 evolutional relations in the primate order were those which appeared to be 

 most susceptible to the inlluences of progressive adaptation. Such inlluenees 

 of evolutional progress do not, however, conline themselves to these more 

 plastic structures. They also aOect certain archaic elements which represent 

 the essential h)undations of neural organization upon which the \ital proc- 

 esses of life depend. Structures, for exam|)le, like the nuclei of the cranial 

 nerves which regulate the action of the heart, the rate and rhythm ol respira- 

 tion, the ]ieristaltic movements of the gastrointestinal canal, the rellex 

 movements of the tongue, lips, nose, soft palate and larynx in acts of swal- 

 lowing, breathing and emission of vocal sounds come into this category. 

 All of them represent the biological framework essi'iitial to the actual process 

 of living. They might for this reason \yv considered to possess an mllexibility 

 both in design and arrangement because of the unchanging nature of the 



