CHAPTER 1 



The circulation and circulation research 

 in perspective 



CARL J. VVIGGERS 



Frank E. Bunts Educational Foundation, affiliated with Cleveland Clinic, 

 Cleveland, Ohio 



CHAPTER CONTENTS 



The Technique of Evaluating Scientific Data 



The Architecture and Function of the Circulatory System 



The Distributing System 



Dynamics of the Arterial System 



Arterioles 



Control of Capillary Blood Flow 



Collecting Veins and Venous Return 

 Adjustment of Cardiac Output to Metabolic Requirements 



Methods for Studying the Determinants of Cardiac Per- 

 formance 



Methods for Determining Cardiac Output in Man 



Venous Return, the Fulcrum of the Circulation 



oldster who has not been pri\ileged to participate 

 actively in circulation research for a number of 

 years. There are both advantages and disadvantages 

 in watching the research game from the sidelines; 

 one is not so close to trivial incidents that perspective 

 is lost, yet one is unaware of how important they 

 may be in determining the final result. Consequently, 

 the present author's considered judgment as to the 

 status of current opinion on many problems may not 

 accord with that expressed in subsequent chapters 

 bv those still active in circulation research. 



THIS CH.\PTER is divided into two sections: the first 

 represents a perspective of the general features of 

 tiie circulatory system and considers some of the 

 vascular mechanisms concerned with the redistribu- 

 tion of blood flow in accordance with regional meta- 

 bolic requirements. The second deals with changes of 

 opinion that have taken place within the memory 

 of the present author with regard to the mechanisms 

 by which cardiac output is nicely adjusted to the 

 vicissitudes of everyday life. The role that improve- 

 ments in methodologies have played are briefly 

 discussed. Since the perspective presented is essen- 

 tially a review of reviews, references are largely re- 

 stricted to surveys made at various periods of the 

 present century that the reader may care to consult 

 as extensions to this brief discussion. 



In perusing this exposition, the reader is warried 

 that it represents the considered interpretations of an 



THE TECH.NIOUE OF EV.'\LU.'^TING SCIENTIFIC Tl.\T.\ 



It has been a part of the present author's philosophy 

 that assessment of current opinion of course requires 

 recognition of new data procured through constant 

 improvement in methodologies. However, it is like- 

 wise important to acknowledge valid discoveries and 

 deductions of the past and to integrate new ones with 

 them. In assessing older data, and doctrines derived 

 from them, an author must constantly remain aware 

 that results once considered crucial have, in many 

 instances, become less certain when viewed in the 

 light of new advances. Further, the interpretation of 

 experimental results, both old and new, depends on 

 the sagacity of the investigator and on the scientific 

 atmospliere at the time. That is to say, investigators 

 acquire diverse senses of values as a result of their 

 scientific training; few are completely free from bias, 

 and many are afflicted with a natural disposition 



