602 Causes and Course of Organic Evolution 



tracing of commencing and advancing mentality amongst the 

 lower animals, and an interpretation at the same time of the 

 acts of the latter, as they pass from simpler to more intricate 

 movements and responses, that a possible explanation may 

 ultimately be got of even the most involved mental acts of 

 the highest animals. This method, already successfully pur- 

 sued in part by Eimer, Lauder-Lindsay, Romanes, and subse- 

 quent workers, has yielded results of lasting value. But, as 

 Washburn (196: 4) has well observed, the anecdotal method 

 alone has always to be used with care. 



Now, in explanation of even the most complex resultant cog- 

 nitic movements, observational evidence has been adduced 

 to show that such can be explained on chemico-physical grounds. 

 If most facts of the case point to a like explanation for cogitic 

 activity even on the highest plane, there is no need to call in 

 an occult or hidden mental agency. 



All higher mental effort is now recognized as involving great 

 expenditures of energy. The lecturer, the author, the financier, 

 the diplomat, the man of wide business affairs, the president 

 of corporations or of nations, after four or five hours of mental 

 effort, experiences a more fagged and depleted bodily state than 

 does the manual worker after three times as many hours of 

 labor. The results accomplished also by brain-workers, within 

 such time, have correspondingly wide influence, and are an 

 approximate index to the high quality of energy expended. 



Such being necessarily true, it follows physically that either 

 very large supplies of the more simple organic food compounds, 

 or moderate supj^lies of some highly complex organic body, 

 should be stored in or around the ganglion cells, and should 

 gradually be used up during mental acts. After prolonged 

 and intense mental activity, therefore, such a material would 

 reach its lowest ebb. Now in rested ganglion cells an abundant 

 reserve of fine aggregated granules — the Nissl bodies or neuratin 

 as we have named such — either crowd the cell substance ir- 

 regularly as amongst many invertebrates cited, or are arranged 

 in concentric layers or in patterns as seems frequently true of 

 vertebrate nerve-cells. The granules become more cloudy, 



