ZOOGENY. 353 



reverse import, although the veins are larger than the 

 thoracic duct. In the investigation of such relations, 

 recourse can by no means be had to quantity or size, 

 but to the importance of the quality or contents. 



1982. The veins are, properly speaking, subordinated 

 to the lymphatic vessels, just as the arteries are to the 

 tracheae, or air-tubes, and the former therefore pass over 

 into the lymphatic vessels. 



c. Circulation. 



1983. Through the veins, as arterio-lymphatic ducts, 

 the vascular system has become a closed system in itself, 

 because, on account of the polarity, the vein unites at 

 both extremities directly with the artery. It is a con- 

 tinuation of the artery, like the air-duct is of the skin, 

 and the lymphatic vessel of the intestine. Thereby a 

 Circulation of the arteriose mucus or blood originates. 



1984. In its essence the circulation is a combination of 

 the intestinal with the branchial system into one anato- 

 mical system. 



1985. The circulation is therefore a higher forma- 

 tion, since through it the vascular system repeats in 

 itself the totality of the vegetable organism. 



1986. On that account the circulation is the vital 

 process proper. 



1987. But for that reason also, the circulation is 

 impossible in the plant, since it is devoid of arteries 

 and veins. 



1988. It makes its appearance in the aquatic animals, 

 for they have, generally speaking, vessels. Molluscs, 

 snails, worms, and crabs already possess a circulation ; 

 it is wanting, on the contrary, in those animals that 

 are without intestine, and ceases in insects, when, or in 

 whom, the air-vessels obtain the preponderance. 



1989. In circulation the galvanism is restricted. 

 In the skin, intestine, air- and lymphatic vessel there 

 is also galvanism, but distributed upon organs that are 

 remote and subservient to different purposes. 



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