HOW WE DEFEND URSEL VES FROM UR FOES 9 5 



appear and therefore how we may either guard our flowers and food- 

 vegetables from their ravages, or remove the parasites when once 

 they have settled on their victims. The loss to farmers, fruit-growers 

 and horticulturists each } r ear through parasites is enormous. 



Fungi and moulds are parastitic on animals as well as on vegetables ; 

 the salmon has the fungoid salmon disease, the grouse has the bacterial 

 grouse disease, the barn-door fowl has its cholera, the swine have 

 swine-fever, the cattle have anthrax and Einderpest, horses " glanders " 

 and so on. 



Then animal parasites infest animals; the frog's lung harbors cer- 

 tain lowly creatures known as Gregarinidse ; dogs, cats, pigs, horses, all 

 have their intestinal parasites, from which obnoxious worms man 

 himself is by no means exempt. 



Host and unbidden guest, victim and parasite — this inter-relation- 

 ship runs through the whole of living nature; it is not the exception, 

 it is the rule. Nature has indeed provided for it ; the intestinal worms 

 of the horse have actually developed an arcii-ferment which prevents 

 their being digested by the digestive ferments of the horse's intestine. 

 Attack and defence, action and reaction unceasingly, this is nature's 

 method; there is no rest; and there is no splendid isolation; we must 

 be attacked and preyed upon and resist — forever! 



A few plants and animals have taken refuge in "protective mim- 

 icry " ; the dead-nettle imitates its stinging neighbor, and so is avoided 

 by such animals as avoid the latter; some insects imitate dead leaves, 

 twigs, etc., and so are not devoured by insect-eating birds. 



But the majority of the foes that man has to battle with are far 

 more subtle than intestinal worms or mosquitoes, or even fungi; for 

 there are myriads of bacteria so light that they float in air even when 

 dust settles; so small that millions can inhabit a drop of water; so 

 numerous that arithmetic is powerless in designating them; so power- 

 ful that they have emptied cities, decimated armies and devasted con- 

 tinents. The mortality of the great Boer War had been a trifling thing 

 if the English had had only to reckon with the Mauser bullets ; far more 

 deadly the typhoid bacilli than all the guns of all the Dutchmen and 

 their allies. 



It is now common knowledge that nine out of ten diseases have an 

 actual, physical recognizable source or cause in some particular parasitic 

 bacillus (rod-like form) or coccus (round form). Undoubtedly some 

 diseases are due to microscopic animal forms, such as ague (malaria), 

 yellow fever, dysentery, the sleeping sickness; but the vast majority are 

 due to vegetable parasites of microscopic size. All those serious dis- 

 eases known as diphtheria, typhoid fever, cholera, plague, tuberculosis, 

 pneumonia, influenza, rheumatism, common cold, and infantile paraly- 

 sis, have been shown to be due to the living body being invaded by 

 countless numbers of infinitely minute rod-like or ball-like microbes. 



