MICROSCOPIC COMPOSITION OF THE BODY. 19 



very imperfectly carried out even in the most advanced 

 communities, and we accordingly hear from time to time 

 of the over-production of this or that article ; but it is in 

 part effected through the agency of capitalists who control 

 the activities of many individuals in accordance with what 

 they think to be the quantity of various articles likely to 

 be required from time to time. 



Exactly similar phenomena result from the division of 

 physiological labor in the human body. Each tissue and 

 organ doing one special work for the whole body, and rely- 

 ing ou the others for their aid in turn, every sort of 

 necessary work is better performed ; the tissue or organ, 

 having nothing else to look after, is constructed with 

 reference only to its own particular duty, and is capable of 

 doing it extremely well. This, however, necessitates a 

 distributing mechanism by which the excess products, if 

 any, of the various organs, shall be carried to others which 

 require them ; and a regulating mechanism by which the 

 activities of each shall be controlled in accordance with 

 the needs of the whole body at the time being. We accord- 

 ingly find a set of organs, the heart and blood-vessels, which 

 carry blood from place to place all over the body, the 

 blood getting in its course something from and giving 

 something to each organ it flows through ; and a set of 

 nervous organs which ramify in every direction and regu- 

 late the activity of all the more important parts. 



Tlie chemical composition of the body. If we go be- 

 yond the tissues to seek the ultimate constituents of the 

 body, we must lay aside the microscope, and call in chem-. 



How does the division of duties in it affect the human body? 

 What is the object of the distributing mechanism? What of the 

 regulating? What are the distributing organs in the body called? 

 What is the object of the nerve organs? 



