A Mode of Communication
Like players on a team, the individual cells of an animal's body must communicate with one another, to ensure the proper functioning of the whole. Hundreds of decisions must be made and communicated throughout the body every minute. Methods of communication between cells fall into four broad categories:
The endocrine system consists of the endocrine hormones and the glands that produce them.
Audesirk, T., Audesirk, G. and Byers, B. (2011). Biology. 9th ed. Boston, Mass.: Benjamin Cummings.