PEPPER TREE POLLEN AND HAY FEVER. 339 



only a slight admixture of small fragments of the flower. It is 

 noteworthy that the pollen popularly regarded as causing these 

 epidemics should be so sticky, as according to all the canons of 

 hay fever this character should effectively prevent it from being 

 dispersed through the air. The comparative purity of the pollen 

 prepared in the manner described was probably because no other 

 part of the flower could adhere to the smooth surface of the glass. 



When the neat pollen was applied to the scarified skin it was 

 noticed that the pollen become invisible almost immediately. This 

 is probably to be explained by the dissolution in the blood serum 

 of the oil which occurs on the outside of the pollen grains and bears 

 the pigments which give the pollen its colour. 



It will be noticed on reference to the table that all the patients 

 susceptible to the epidemic reacted either strongly or very strongly 

 to the pollen, whereas no non-susceptible persons gave any reaction 

 whatever, either to the pollen itself or to the other materials 

 employed. The non-susceptible patients were therefore satisfactory 

 as controls, and the conclusion is justified that pepper tree pollen 

 can cause hay fever. 



Saline Extract. 



For the saline extract of pepper tree pollen I am indebted 

 to the South African Institute for Medical Research, Johannes- 

 burg, where the method followed in preparing it was that described 

 by Dr. Scheppegrell, in the U.S. Public Health Reports, Vol. 32, 

 No. 29, July 20, 1917. Considerable difficulty was experienced in 

 obtaining and manipulating the pollen owing to its stickiness, and 

 Dr. Harvey Pirie, of the Institute, writing in regard to the extract 

 states that "when preparing the extract .... I found it very 

 difficult to get the pollen off, the grains appear to be very sticky," 

 and that though "the extract aimed at being a 1 in 10,000 extract 

 of pollen, it was impossible to get the pollen in any quantity 

 separate froiri the flowers," and it "may have been much under 

 1 in 10,000 as regards the pollen." These statements confirm my 

 experience at Bloemfontein with regard to the stickiness of the 

 pollen, and also no doubt partly explain the weak reactions to 

 the extract. 



On reference to the table it will be seen that of the nine 

 susceptible patients who, as has been stated, reacted strongly, or 

 very strongly, to the neat pollen, only four reacted to the extract, 

 and in all cases only very mildly, whilst two of these patients 

 reacted, in the one case as strongly, and in the other case more 

 so, with saline only. It should here be explained that the reactions 

 of patient No. 3 to the reagents other than neat pollen are prob- 

 ably unreliable, as the swelling and reddening resulting from the 

 application of the neat pollen spread so as quickly to envelop the 

 centres at which the other three reagents were applied. Inci- 

 dentally, this experience shows that where more than one centre 

 is being inoculated these should be at some considerable distance 

 apart. 



