188 DUALISM OF FORCES. 



other man, tells us, that after the fecundation of the ovum of 

 any animal, and its division into cells and layers, the organ 

 of circulation proceeds to its incipient development from the 

 middle layer of the germ. " First," the blood appears by a 

 simple process of liquefaction of the cells. It can be seen 

 under the microscope how the particles, or the cells of that 

 layer, begin to loose at the outer margin, and to move between 

 themselves, and to run in particular directions, and to combine 

 into currents, and those currents to assume particular direc- 

 tions, before there is a heart, and before there are blood-vessels. It 

 can be seen in every chicken under so low a magnifying power, 

 that no one should lose the opportunity of seeing this wonder- 

 ful sight. When blood corpuscules move from the center toward 

 the margin of the germ [Expansion], the other cells, which be- 

 come loose in the periphery of the germ, begin to move toward 

 the center [Contraction]. In the beginning, there being no cur- 

 rent circulating, the two collections of fluid meet, and finally 

 become regular currents, by means of channels through which 

 the blood runs for a regular circulation* 



These fundamental, expansive, contractive, and circulatory 

 motions are subsidiary to the development of a fourth opera- 

 tion, by which affinitized particles floating in the circulating 

 menstruum are brought into conjunction, and deposited in the 

 form of solid tissues. They are at first aggregated on all 

 sides of the circulating channels, and form the blood-vessels, 

 the ramifications of which (says Agassiz) are at first constantly 



* Agassiz'a Lectures on Comparative Embryology. Here we have, in the words of 

 one who wrote without any view to the distinctive philosophy of the present treatise, an 

 illustration of the successive origins of the laws of Expansion, Contraction, and Circu- 

 lation. Considering these facts and principles as equally applicable, on a large acale, 

 to the great fecundated germ or ovwn of the cosmical creation, it will illustrate per- 

 fectly the incipient process by a prolongation of which the universe received its present 

 mature form. 



