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ZOB 



A BIOLOGICAL JOURNAL 



Vol. I. APRIL, 1890. No. 2. 



THE ECONOMY OF NATURE AS EXEMPLIFIED BY 



VEGETABLE AND ANIMAL PARASITES. 



BV H. H. BEHR. 



The ancients, by a kind of intuition or instinctive knowledge of 

 the general fitness of things, expressed their admiration »'f the 

 universe by the phrase " the harmony of the spheres," and >ome 

 even went so far as to beheve in strains of music produced by the 

 rotation of celestial bodies. It has since been proved that mathe- 

 matical laws govern the infinite space. We leave the study of those 

 laws to the astronomer and restrict our attention to the beautiful 

 harmony that rules the organic creations peopling our earth. 



We see here first the antagonism between animal and vegetable 

 life, and observe at the same time that each is necessary to the ex- 

 istence of the other. As there is no shadow without light and 

 vice versa^ so no animal life can exist without plant, no vegetable 

 life without animal. We see animal and plant by their respiring 

 process absorb oxygen and secrete dioxide of carbon. We observe 

 that, with the sole exception of those plants entirely destitute of 

 chlorophyll, an opposite process takes place in the nutrition of the 

 plant, by which it absorbs the carbon of the dioxide and sets the 

 oxygen free. As this process of nutrition is considerably more 

 active than the exceedingly slow one of vegetable respiration, prac- 

 tically the plant secretes oxygen and absorbs carbon. 



Any aquarium illustrates this natural dependence of animal and 

 plant. Practically the experiment could be made in a very simple 

 way with two glass globes containing gold fish. If there are intro- 

 duced into one some rooting branches of watercress it will be 

 seen that the water keeps fresh and respirable to the fish, the water- 



cress secreting the supply of oxygen necessary to sustain animal 



respiration and absorbing the carbon from the dioxide of carbon 



