238 SCIENCE PROGRESS 



evil effects as loss of Vitamin A, while the violet rays of the sun 

 occasion the same good effects as its restoration to the food. 



It is manifestly much too early to draw any sort of con- 

 clusion from those very fascinating studies. Yet the curious 

 fact of the publication of these two discoveries within a few 

 weeks of each other may be commented on. If light may be 

 food, it may also, in a different form, amount to starvation. 



The Cancer Research report deals also with attempts to 

 grow various tissues in vitro. This was not found to be pos- 

 sible unless there had been added to the culture fluids an 

 embryonic substance of unknown composition. In the pre- 

 sence of this substance growth took place. Yet, so far as 

 parenchymatous tissues were concerned, no differentiation 

 could be detected unless and until connective tissue elements 

 were present. A vast field is opened up here. 



Another interesting piece of work was that which culmin- 

 ated in the discovery that cancer cells appear to produce some 

 body exercising a highly poisonous effect on them. Thus, if 

 the piece of malignant growth is not removed at frequent 

 intervals to new media it perishes. Curiously enough, normal 

 tissue is not affected in this way and will continue to grow on 

 media where cancer has been growing, but in which it cannot 

 longer maintain itself. Efforts are being made to determine 

 the nature of this poison, which seems to possess the important 

 quality of killing cancer cells but not the normal cells of the 

 organism. 



EDUCATION. By A. E, Heath, M.A., University, Liverpool. 



The writer of these notes has received certain comments on 

 the remarks (Science Progress, July 1920, p. 47) concerning 

 the relation between the personality of the teacher and the 

 improvements in method which come from educational experi- 

 ment and research. It was there contended that " personality " 

 — ^which involves the same elements of self-control that are 

 reflected in the control of subject-matter we call method — is of 

 co-ordinate importance with the rational study of educational 

 processes. The basis of the criticism is the statement that this 

 view does not give to personality the place to which its funda- 

 mental importance entitles it. " A teacher," it is claimed, 

 " either has or has not a suitable personality which is his 

 irrespective of the methods he uses and which is a product 

 crystallising out of the whole man's * attitude ' or ' philosophy ' 

 or ' religion.' " Now I am at one with the critic in believing 

 in the importance of personality ; but I am not happy about 

 the implied disjunction between the teacher's personality and 

 his methods. I cannot agree that, somehow or other, an attitude 



