CHAPTEE VI 



THE CIRCULATION OF THE BLOOD : ITS DISCOVERY 



CONTENTS. 1. Physiological necessity for the circulation of the blood. Schema 

 of cardie-vascular system. 2. Theory of Galen. 3. Discovery of the lesser cir- 

 culation ^question of the priority of Columbus, Servetus, and Vesalius. 4. Dis- 

 covery of the general circulation by Cesalpinus. 5. Completion of the work by 

 Harvey. 6. Discovery of the lymph circulation by Eustachius, Aselli, Pecquet, 

 Rudbeck, Bartholin. 7. Discovery of the capillary system, and direct observation 

 of the circulation by Malpighi. 8. Microscopic observations of the phenomena of 

 circulation : Spallanzani, Poiseuille, R. Wagner, etc. 9. Discovery of diapedesis 

 of blood-corpuscles and migration of leucocytes : Waller, Addison, Recklinghausen, 

 Cohnheim. Bibliography. 



THE Blood, in order to fulfil its physiological task as centre 

 and agent of the metabolic exchanges of the whole body, 

 must be in perpetual motion within the vascular system which 

 contains it. If the blood remained stagnant, that portion of it 

 which lay within the capillaries of the pulmonary system might 

 indeed become saturated with oxygen, but would be unable to 

 conduct it to the parts where it is required, i.e. to the parenchyma 

 of the organs ; on the other hand, the portion contained in the 

 capillaries of the aortic system would become charged with carbonic 

 acid which could not be exhaled from the body. The blood of the 

 capillaries leading to the portal veins would become charged with 

 the nutritive materials taken up from without, but would be 

 unable to reach the organs that require feeding; while the 

 products of consumption, again, would accumulate in these organs, 

 since they could not reach the organs of excretion. 



I. Owing to the intensity of metabolism necessary to the 

 maintenance of the principal vital functions, especially in the 

 higher animals, the arrest of the movements of the blood leads in 

 a few moments to death from asphyxia of all the tissues. The 

 vascular system is therefore provided with a pumping apparatus, 

 which serves to keep the blood in continuous rapid movement in 

 all parts of the body. 



If we reduce the cardio-vascular system to a schema (Fig. 45), 

 we may distinguish anatomically a central organ, and the arterial, 

 venous, and capillary systems : physiologically, a right or venous, 



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