CEREBRAL HEMISPHERES AND MEMORY 253 



than a | n NaCl solution. As soon as the heart be- 

 gins to beat, the KC1 becomes much more poisonous 

 than the NaCl solution. A similar discontinuity is 

 noticed if we try the effects of lack of oxygen. As 

 soon as the circulation begins, the Funclulus embryo 

 becomes quite suddenly much more sensitive to a lack 

 of oxygen. The functional changes in the embryo 

 itself are sudden and not gradual or continuous. The 



o 



heart-beat, for example, starts at a certain time, sud- 

 denly, after a certain stage of development has been 

 reached. 



The idea of a steady, continuous development is in- 

 consistent with the general physical qualities of proto- 

 plasm or colloidal material. The colloidal siibstances 

 in our protoplasm possess critical points. If we in- 

 crease the pressure of a gas below a certain tempera- 

 ture, at a certain critical point the gas becomes 

 liquid. The colloids change their state very easily, 

 and a number of conditions- -temperature, ions, en- 

 zymes are able to bring about a change in their state. 

 Such material lends itself very readily to a discon- 

 tinuous series of changes, while a gradual steady 

 development, such as most Darwinians assume, is 

 practically excluded. 



We, of course, concede that the associative memory 

 shows different degrees of development or perfection 

 in different animals. These different degrees are 

 mainly differences in capacity and resonance. By 

 difference in capacity I mean a difference in the 

 number of associations of which the brain is capable. 



