34 THE HUMAN BODY. 



tribution employments. It is extremely desirable that means 

 shall be provided by which it may receive information of ex 

 ternal changes which may affect it as a whole, such as the 

 policy of foreign countries; or which shall enable the inhabi- 

 tants of one part to know the needs of another, and direct 

 their activity accordingly. Foreign ministers and consuls and 

 newspaper correspondents are employed to place it in com- 

 munication with other states and keep it informed as to its 

 interests; and we find also organizations, such as the meteor- 

 ological department, to warn distant parts of approaching 

 storms or other climatic changes which may seriously affect 

 the pursuits carried on in them. In the Human Body we 

 have a comparable class of intelligence-gaining tissues lying 

 in the sense-organs, whose business it is to obtain and com- 

 municate to the whole information of external changes which 

 occur around it. Since the usefulness of these tissues 

 depends upon the readiness with which slight causes excite 

 them to activity, we may call them the irritable tissues. 



6. CO-ORDINATING AND AUTOMATIC TISSUES. Such in- 

 formation as that collected by ministers in foreign parts or by 

 meteorological observers is usually sent direct to some central 

 office from which it is redistributed; this mere redistribution 

 is, however, in many cases but a small part of the work carried 

 on in such offices. Let us suppose information to be obtained 

 that an Indian chief is collecting his men for an attack on 

 some point. The news is probably first transmitted to Wash- 

 ington, and it becomes the duty of the executive officers there 

 to employ certain of the constituent units of the nation in 

 such definite work as is needed for its protection. Troops, 

 have to be sent to the place threatened perhaps; recruits en- 

 listed ; food and clothes, weapons and ammunition, must be 

 provided for the army; and so on. In other words, the work 

 of the various classes composing the society has to be organ- 

 ized for the common good ; the mere spreading the news of 

 the danger would be of little avail. So in the Body: the 

 information forwarded to certain centres from the irritable 

 tissues is used in such a way as to arouse to orderly activ- 

 ity other tissues whose services are required ; we find 

 thus in these centres a group of co-ordinating tissues, 

 represented by nerve-cells and possibly by certain other 

 constituents of the nerve-centres. Certain nerve-cells are 

 also automatic in the physiological sense already pointed 



