ANALOGY BETWEEN THE CIRCULATIONS. 403 



lion, ho further points out, that the number of them which 

 in a considerable interval flows through the great centres, 

 is enormous when compared with their absolute number ; 

 just as the quantity of money which annually passes 

 through the great mercantile centres, is enormous when 

 compared with the total quantity of money in the kingdom. 

 Nor is this all. Liebig has omitted the significant circum 

 stance, that only at a certain stage of organization does this 

 clement of the circulation make its appearance. Through 

 out extensive divisions of the lower animals, the blood con 

 tains no corpuscles ; and in societies of low civilization, 

 there is no money. 



Thus far, we have considered the analogy between the 

 blood in a living body and the consumable and circulating 

 commodities in the body politic. Let us now compare the 

 appliances by which they arc respectively distributed. Wo 

 shall find in the development of these appliances, parallel 

 isms not less remarkable than those above set forth. Al 

 ready we have shown that, as classes, wholesale and retail 

 distributors discharge in a society, the office which the 

 vascular system discharges in an individual creature ; that 

 they come into existence later than the other two great 

 classes, as the vascular layer appears later than the mucous 

 and serous layers ; and that they occupy a like intermedi 

 ate position. Here, however, it remains to be pointed out 

 that a complete conception of the circulating system in a 

 society, includes not only the active human agents who 

 propel the currents of commodities, and regulate their dis 

 tribution ; but includes, also, the channels of communication. 

 It is, the formation and arrangement of these, to which we 

 now direct attention. 



Goinsr back once more to those lower animals in which 



CJ . 



there is found nothing but a partial diffusion, not of blood, 

 but only of crude nutritive fluids, it is to be remarked that 

 the channels through which the diffusion takes place, aro 



