272 Agricultural Gazette of N.S.W. [April 3, 1920. 



the plant is eaten, becomes absorbed into the system and renders unpigmented 

 or white skin peculiar!}' sensitive to sunliglit, with the result that on exposure 

 to the sun sucli skin is injured, as evidenced by the reaction described ; the 

 excoriation, bleeding, <fec., and indirect results of the general injury being 

 inflicted by the animal itself in the effort to relieve the intolerable itching. The 

 reaction is much more than mere sunburn, especially as the condition -is not 

 seen in similar animals exposed to greater sunlight, but not fed on this or 

 other skin-sensitising substances. The condition is (juite comparable to that 

 produced by feeding on trefoil previously desciibed by the writer, save that 

 the effects produced by St. John's Wort are far more serious than those seen 

 in trefoil sensitisation. 



Besides the skin affection, St. John's Wort appears to exert an effect upon 

 the central nervous system, usually causing great mental depression, but at 

 times an exactly opposite effect, that is, excitement which sometimes becomes 

 almost mania. 



There is no reason to doubt that pigmented skin is sensitised just as much 

 as unpigmented skin, but the colouring matter in the former prevents the 

 sun's rays from acting upon it and thus no injui'y results. This is shown by 

 the fact that if unpigmented or white skin is stained or coloured, no reaction, 

 to that skin occui's, although the animal may be .sensitised and it is exposed: 

 to sunlight. 



8o far as treatment is concerned, the only one of value is that of prevention. 

 The foremost object should be the eradication, or where that is imprac- 

 ticable, the keeping within bounds of the cause — St. John's Wort. Witb 

 horses and cattle on infested areas the trouble may be averted by treating 

 the white parts with a dark staining liquid, which should be non-poisonous in 

 case the animal should lick the part. With sheep, such a procedure would; 

 be complicated by the facts that — (1) the whole of the body would have to- 

 be treated : (2) the number of animals to be so treated would be large ; and 

 (3) the possibility of injury to the fleece. These considerations might find the- 

 proposition inpracticable. Whether the local treatment of the skin would 

 prevent the brain symptoms or the injury to the eyes which often occurs are; 

 also matters of doubt. 



Correcting Acidity caused by Superphosphate. 



Does the continuous use of superphosphate tend to sour the soil ? This-- 

 question was recently addressed to the Department by a Pokolbin orchardist 

 and replied to by the Chief Inspector of Agriculture as follows : — 



The continuous use of superphosphate will tend to increase the acidity of 

 soil and may consequently be detrimental to its fertility, but the sourness 

 can easily be remedied by the application of lime. Lime should be applied 

 at the rate of 1 ton per acre about a nionth or six weeks before the usual 

 time for applying the superphosphate. 



