26 Alfred J. Eivart : 



The poisoning theory of Bitten Pit. 



A satisfactory theoiy in regard to a disease or det'eet shoidd : — 



(a) t'oincide with all the facts. 



(b) The suggested agency should be able to produce th& 



disease or defect experimentally. 



(c) The artificially and the naturally produced disease or 



defect should behave with approximate siiiiilarity under 

 'corresponding external conditions. 



In regard to (a) the poisoning theory agrees with all that we 

 knew in regard to the action of ferments, to the sensitivity of the 

 jjulp cells to jDoison, and to the variation of their sensitivity with 

 age, so that an amount of poison at first sufficient to arrest ferment 

 activity would become generally toxic when the protoplasm readied 

 a certain age. In regard to (b) it has been shown that every 

 symptom of bitter pit, including external appearance, colour, 

 character of dead cells and cell walls, and presence of starch grains- 

 can be produced by artificial jjoisouing. The last feature, on which 

 so much stress is usually laid, is a general but not an unavoidable 

 accompaniment of bitter pit. Any agency, including mechanical 

 injury which kills the cells while packed with starch, will cause dead 

 starch-containing tissue to be present in the apple pulp. If, how- 

 ever, the poisoning takes place before the starch has been deposited 

 oi' after it has been dissolved, the dead bitter i»it tissue will not 

 contain any more starch than the living pulp. 



In the early proteid stage of the apple, the cells are resistant 

 to poison, and owing to the rapid cell multiplication and proteid 

 growth, no concentration of absorbed traces of poison is possible. 

 In the starch stage the cells are still resistant, and diastatic 

 activity is the first function to be affected. Odd cells here and there 

 are to be found in the pulp of most sound apples in which the 

 starcli grains have remained undissolved, but in which the poison- 

 ing progresses no furtlier until the general pulp is approacliing 

 death. The reason why l)itter pit is generally accompanied by 

 cells packed with starch is because it is when proteid growth has 

 ceased, that a concentration of al)S()rbed traces of poison liecomes 

 possible, and because the sensitivity to poison increases from this 

 stage onwards in the life of an apple. 



It is in ro;.'ard to tlie unalytii'al evidenc-e that the greatest 

 difficulty of complete proof is to be expected. The tests t'urricd 

 out in conjunction with the Federal Analyst have shown that 

 it is possible to produce artificial bitter pits witli traces of 

 poison so small as to be incapable of detection even by deli- 



