238 THE ASCENT OF MAN 



country into a world of water. The glaciers, under 

 the new conditions, retreat into the mountains, the 

 vesture of ice drops into the sea, a garment of 

 greenness clothes the land. So, in the animal 

 world, a very small rise beyond the animal maxi- 

 mum may open the door for a revolution. With 

 a brain of so many cubic inches, and so many 

 pounds of brain matter, we have animal intelligence. 

 Everything below that limit is animal, and the 

 number of inches or pounds below it makes no 

 difference. But pass to a brain not a few but 

 many pounds heavier, many cubic inches larger, 

 and very much more convoluted, and it is conceiv- 

 able that in passing from the lower to the higher 

 figures some such change might occur as that 

 which differentiates solid from liquid in the case of 

 water. What the chemist calls a " critical point " 

 might thus be passed, and from a condition associ- 

 ated with certain properties — though in the brain 

 we must speak of accompaniments rather than pro- 

 perties — a condition associated with certain other 

 properties might be the result. Thus, as Cope says, 

 "some Rubicon has been crossed, some flood-gate 

 has been opened, which marks one of Nature's 

 great transitions, such as have been called * expres- 

 sion-points ' of progress." A slight rise in intelli- 

 gence might lead to the first acquisition of Speech, 



