340 PEPPER TREE POLLEN AND HAY FEVER. 



As this was only a preliminary attempt at preparing the 

 extract in which there was no evidence as to the strength required 

 and in which the peculiar difficulties of this particular pollen has 

 not been entirely overcome, it is perhaps not surprising that the 

 extract did not react better. But even apart from this, a con- 

 sideration of the biochemistry of the pollen grain leaves doubt 

 ay to whether the method of preparation (which is a standard one) 

 can always achieve what is aimed at. According to the prevailing 

 opinion hay fever is due to toxic proteids contained in the pollen 

 grain, and these the extract aims at bringing into solution; but, 

 as Mr. Philip Smith (1920) has pointed out, these proteids being 

 colloids, are unable to pass through the cell walls of the pollen 

 grain and would only escape if the pollen grains burst. This 

 being so, it seems essential that the solvent used in preparing the 

 extract should be one in which the pollen concerned burst freely. 

 I have tested the behaviour of pepper tree pollen in this con- 

 nection and find that whilst the grains burst freely in water their 

 behaviour in salt solution is variable, but, speaking generally, 

 whilst a small proportion burst in normal saline (0.9 per cent, 

 strength), only very few do so in 5 per cent., which is the strength 

 used in Dr. Scheppegrell's method to extract the pollen. 



Oil Emulsion. 



Observations at Bloemfontein extending over two hay fever 

 seasons had convinced me that pepper tree pollen could cause the 

 disorder. The question, then, naturallv arose as to whether part, 

 at least, of the virulence of this epidemic type of hay fever is not 

 due to the irritating oily and resinous substances which are well 

 known to occur in the pepper tree, and some of which may also 

 occur in the oil found on the outside of the pollen. Indeed, severe 

 skin poisoning is well known to be caused by several species of 

 Rhus (a genus belonging to the same family as, and nearly related 

 to the pepper tree), especially by 11. toxicodendron, the poison 

 ivy, and B. venenata, the poison elder. According to Philip 

 Smith (1920), Pfaff (1897) has succeeded in isolating the poisonous 

 principle — a very sticky, non-volatile oil, which in these plants 

 occurs not only on the stem, leaves and fruit, but also on the 

 pollen. Such an oil would not be extracted by soaking the pollen 

 in 5 per cent, saline. 



The solution of this oil and its presentation to the patient 

 in a non-irritating medium was attempted by my colleague, Dr. 

 M. Rindl, Professor of Chemistry, who, after soaking the pollen 

 in ether until the yellow oil was dissolved off the grains (a few 

 i-econds only), filtered the extract and dropped it slowly into a 

 hot solution of sodium carbonate (0.5 per cent, strength), the 

 object being to form an emulsion of the oil and at the same time 

 drive off the ether, which is a skin irritant. As will be seen from 

 the table, the results were virtually negative. One negative result, 

 however, proves nothing : the question could only be settled by 

 repeated experiments with extracts prepared in several different 

 ways and of various strengths, and preferably from which proteids 



