174 THE PATHOLOGY OF POLLEN IN /ESTIVIS, 



would fall to the microscopist. If density were added, this would 

 cover all. 



A word as to the conveyability of material particles by the 

 atmosphere. There is something ad captanduiii in the splurge of 

 the lugubrious poet : — 



" The dust we tread upon was once alive." 

 But, in the present tense, how true is this of the dust we breathe ! 

 (.\an we not recall the painful interest excited by Tyndall's experi- 

 ments on the impurities of the atmosphere? And, for our 

 purpose, how easy to repeat some of them I Let a beam of sun- 

 light through a hole in the shutter enter a dark room. It ajipears 

 as a slanting, living column. I say living, for every particle seems 

 in motion, due to the incessant dancing movements of millions of 

 motes. 



If now a small spirit-flame, yielding no smoke, be held under 

 this beam, there will soon be seen a dark hole right through the 

 column. Withdraw the flame, and soon the contiguous motes 

 dance into it ; it is again illumined, and the dark hole disappears. 

 If now we pass a red-hot bar through it, the beam will be divided 

 into two parts by a black space. The bar withdrawn, soon the 

 neighbouring motes dance into it, and the beam is all light 



agam. 



The deduction, for our purpose, is that the so-called impurities 

 present are chiefly organic, and the heat lun-ns them out. The 

 spores, infusoria, and microbic matter are thus destroyed — the air 

 literally being purified by fire. 



All these things, even the mineral matter, constitute the aerial 

 dust so distressing to the sufferer from Hay-Fever. And I hold 

 that a prominent irritant in the air, during the Hay-Fever season, 

 is pollen. 



But what is pollen ? It is the fertilizing granule produced by 

 the stamens of a flower. These granules vary greatly in size and 

 form in the different flowers. Some are smooth, others are angu- 

 lar, but those, with which this discussion wifl deal, are globular or 

 elliptical, spiny, and very minute. Not noticing the pollen of the 

 grasses, which particularly affect the early forms of the disease, 

 perhaps the most mischievous of the pollens are those of the Rag- 

 weed and the Golden-rods. I have here specimens of the plants : 



