Cross-Circulation as a Physiological Method

Abstract

IN the mutual co-ordination and integration of the physiological processes in a complex organism, in which actions exerted by the environment on a par ticular part affect the whole and the functional activity of one organ has its influence on numerous others, there are two chief methods adopted. One is by means of the central nervous system, in which messages received from the periphery along certain nervefibres are reflected back, as it were, to outgoing nervefibres, setting into play the appropriate muscular or other response, it may be in a distant part of the organism. This method has been compared to a telephone exchange. The other is by means of the blood. Owing to the continual circulation of the same mass of liquid through all parts of the body, it. will readily be seen that a chemical substance, produced in any one part and passing into the blood-vessels supplying this part, must be carried, sooner or later, to all other parts, and give rise to effects in any tissue or organ sensitive to it. We have here an actual trans port of material, the materials carried, when they result in changes in distant organs, being known as “chemical messengers” or “hormones.”