: * 2 MODERN SCIENCE READER 



of its normal metabolism furnishes material to the blood 

 that is of importance in regulating the activities of other 

 tissues. This idea found a general support in the facto 

 brought to light in relation to the physiological activities 

 of the so-called ductless glands, and subsequently in the 

 series of remarkable discoveries which we owe to the new 

 zeienee of immunology. In recent years it has been re- 

 ifated in attractive form by Sehiefferdecker in his theory 

 of the symbiotic relationship of the tissues of the body. 

 According to this author we may conceive that among the 

 tissues of ft single organism the principle of a struggle for 

 existence, which is so important a* regards the relations of 

 one organism to another, is replaced for the most part by 

 a kind of symbiosis, such that the products of metabolism 

 in one tissue serve as a stimulus to the activities of other 

 fisfwg. If a muscle is stimulated to greater growth by an 

 excess of functional activity the substances given off to the 

 blood during its metabolism act favorably upon the growth 

 of other muscles which are not directly concerned in the 

 increased work, or upon the connective tissue surrounding 

 and permeating the muscular mass; and conversely, the 

 development of connective tissue from any cause aids 

 directly by its secretions or excretions in the growth of the 

 muscle. There is thus established ft circulu* benignug by 

 means of which each tissue profits from the functional 

 activity of its fellow tissues. From many sides and in 

 many ways facts have been accumulating which tend to 

 impress the general truth that the co-activity of the organs 

 and tissues may be controlled through chemical changes in 

 tb<; liquid midia of the body, as well as through nerve im- 

 pulses, but in physiology at least we owe the definite formu- 

 lation of this point of view to Bayliss and Starling, 

 Through their investigations upon secretin they obtained 

 an explicit example of how one organ controls the activity 

 of another organ by means of a specific chemical substance 

 given off to the blood Other facts known in physiology 

 fa refUfd to HM internal itcretfofu were easily brought, into 



