BIOLOGY IN ITS WIDER ASPECTS 1259 



and finally they become more or less blind. To what is this extra- 

 ordinary condition due? According to our best authority, Prof. 

 W. M. Wheeler, the physogastry is due to the fact that the beetles 

 are living in darkness, stagnancy, humidity, and airlessness, and that 

 the hosts insist on feeding them over-abundantly with carbohydrates. 

 A parable indeed. 



There remains the organism, which is a product of hereditary 

 nature played upon by nurture. What can we say? Of much 

 interest is Karl Pearson's pamphlet, not very clearly titled The 

 Right of the Unborn Child. It does not really deal with that 

 subject at all, it deals with the duty of not allowing certain kinds 

 of children to be bom. The point is this, that Karl Pearson took 

 one thousand boys from one school in London and investigated 

 their eyes, or got some expert to do so. He tells us in great detail, 

 we are sure with perfect accuracy, what was wrong with the eyes 

 of many of these boys — a lack of sphericity in the cornea of the eye 

 and a lack in the adjustments which secure that the image formed 

 by the lens is thrown immediately on the retina, and not in front of 

 it. When the image is not projected precisely on the right place, 

 there is a diminished acuity of vision. This implies astigmatism — an 

 inability, for instance, to see the blackboard clearly, an inability for 

 which the fathers or even the grandfathers of these boys were 

 responsible. Nowadays the school physician detects the astigmatism, 

 and the boys are given spectacles. But that is not the point. Out of 

 the one thousand boys in that one school, 222 suffered from severe 

 astigmatism. That seems very alarming, especially as it is only an 

 example of the kind of thing that is happening everywhere. Prof. 

 Pearson makes the point that the 222 boys were so badly astigma- 

 tised that none of them could have survived in prehistoric times, 

 for they could not have seen the enemy or the booty. For huntsmen 

 in palaeolithic times it was all-important to see with precision the 

 animal hunted; they had to slay it or else be slain; selection for 

 clear vision was stringent. But nowadays we supply the optically 

 defective with spectacles, and, although they cannot enter the 

 Army or Navy, they can adopt many professions. They flourish and 

 have children like themselves, and so the number of cases of 

 astigmatism goes on increasing. Selection for clear vision has 

 largely ceased. This is a parable too, because there are other 

 defects, even more serious than astigmatism, which are increasing 

 the burden of deficiency that we are handing on to the next 

 generation. 



But our main point is to explain the biological prism, and to 

 show how, by getting into the habit of thinking of all the three sides 

 of a spherical triangle, we may avoid mental astigmatism, which is 

 as undesirable as the physical. 



