Chap. I. PARASITIC ANIMALS. 123 



luer iulialo atmospheric air, and exhale carbonic acid gas, the latter appropriate 

 carbon and exhale oxygen, it was not until Dumas and Bousingault' called partic- 

 ularly the attention of naturalists to the subject, that it -vvas fully understood how 

 direct the dependence is of the animal and vegetable kingdoms one upon the other, 

 in tliat respect, or rather how the one consumes what the other produces, and viee 

 versa, thus tending to keep the balance which either of them would singly disturb 

 to a certain degree. The common agricultural practice of manuring exhibits from 

 another side the dependence of one kingdom upon the other : the undigested 

 jiartieles of the food of animals return to the ground, to fertilize it for fresh pro- 

 duction." Again, the whole animal kingdom is either dii-ectly or indirectly dependent 

 upon the vegetable kingdom for its sustenance, as the herbivorous animals afford 

 the needful food for the carnivorous tribes. We are too far from the time when 

 it could be supposed that Worms originated in the decay of fruits and other vege- 

 table substances, to need here repetition of what is known respecting the repro- 

 duction of these animals. Nor can it be nece.s.sary to show how preposterous the 

 assumj^tion would be that physical agents produced plants first, in order that from 

 these, animals might spring forth. Who coidd have taught the physical agents to 

 make the whole animal world de2)endent upon the vegetable kingdom? 



On the contrary, such general facts as those above alluded to, show, more directly 

 than any amount of special disconnected facts could do, the establishment of a well- 

 regulated order of things, considei'ed in advance ; for they exhibit well-balanced 

 conditions of existence, prepared long beforehand, such as only an intelligent being 

 could ordain. 



SECTION XXX. 



PARASITIC ANBLAXS AND PLANTS. 



However independent of each other some animals may appear, there are yet 

 many which live only in the closest connection with their fellow-creatures, and 

 which are knoA\Ti only as parasites upon or within them. Such are the intestinal 

 Worms, and all the vermin of the skin.'' Among plants, the Mistletoe, Orobanche, 



* Dumas, LcQon siir l:i st.atique chimique Acs 1 .ind 2 ; see also Rcdolphi, (K. A.,) Entozoorum 

 etres organises, Ann. Sc. Nat. 2de ser. vol. G, p. 33; sive Vermium, etc., q. a., p. 31. — Bkemser, (J. G.,) 

 vol. 17, p. \'2'2. Ueber lebende Wiirmcr im lelx'nden Mt-nsohen, 



' LiEBiu, Agricultural Cliemistry ; Animal Chum- Wien, 1819, 4fo. — Dujahdin', (F.,) Hist. Nat. des 

 istry. Ilelminthes, etc., q. a., p. 32. — DiESiXG, (C. M.,) 



* See above, p. 7G, notes I and 2, and p. 77, notes llistoria Vermium, etc., ([. a., p. 32. 



