126 CHANGES IN THE CIRCULATION. 



cility of escape. So also the cells have been known, in cases of chloro- 

 sis, to sink to one fifth of the healthy amount. The albumen, too, ex- 

 hibits like variations. In Bright's disease it greatly diminishes, much 

 of it escaping in the urine by the straining action of the kidneys. 



Thus constituted, the blood, by a mechanism to be described in the 

 Chan es occur next cna P ter passes from the heart alternately to all parts 

 ring during the of the system, and alternately to the cells of the lungs, giv- 

 circuiation. -^ T ^ Q ^ Q what have been termed the greater and less cir- 

 culation, or the systemic and the pulmonary. In the systemic circula- 

 tion, the blood, which leaves the heart in an arterialized condition, or as- 

 sociated with atmospheric oxygen, gives up that element to the various 

 tissues as it pervades them, and accomplishes a double result: the re- 

 moval of all those particles which, having discharged their duty and un- 

 dergone partial or perfect interstitial death, are ready to pass away, and 

 also the liberation of a great amount of heat by the destructive oxidation ; 

 so, at the same time, the wasted matter is removed and advantage taken 

 of it to raise the temperature of the body. This done, the blood makes 

 its way back to the heart, following the channel of the veins as they suc- 

 cessively converge into trunks that are larger and larger. At the mo- 

 ment of surrendering its oxygen and receiving the various products of 

 combustion, a change of color occursr The bright crimson turns to a 

 deep blue, and the blood presents itself of that color at the heart. 



It now undergoes the less or pulmonary circulation. Leaving the 

 heart, it passes over the air-cells of the lungs, and is there exposed to the 

 aerating action of the atmosphere. From the interior of the cells the 

 discs receive their supply of oxygen, the plasma surrendering up carbonic 

 acid and the vapor of water. The color now changes back from the 

 blue to the scarlet. In this condition it returns to the heart, to be dis- 

 tributed in the systemic circulation once more. 



During this double round an incessant change is taking place in the 

 Less obvious constitution of the'blood: it is undergoing a continuous met- 

 but important amorphosis. In some respects, as, for instance, in color, 

 this is obvious enough. But the invisible changes infinite- 

 ly exceed in importance and amount those that are obvious to the eye. 



All the soft tissues, since they are wasting away, require repair. 

 This, inasmuch as it is accomplished either directly or indirectly by the 

 albumen of the blood, gives rise to a constant drain of that substance, 

 and demands a constant supply, which is provided by nutrition or stom- 

 ach digestion. 



The cells, which constitute the other chief portions of the blood, are 

 Translation of necessai T * tne production of a high temperature, by con- 

 oxygen by th stantly transferring oxygen from the cells of the lungs to 

 cells. every part of the body ; carriers of oxygen they have been 



