292 OF THE CIRCULATION OF THE BLOOD. 



ducing treatment may appear to be, its remote effects are much to be dreaded. 

 And when the results of a large arid varied experience are brought together, 

 the Author believes that those will be found most satisfactory in which the 

 treatment has been moderately evacuaut, and early susteutative. 1 



CHAPTER VIII. 



OF THE CIRCULATION OF THE BLOOD. 



1. Of the Circulation in General. 



230. THE Circulation of nutritive fluid through the body has for its object, 

 on the one part, to convey to every portion of the organism the materials 

 for its growth and renovation, together with the supply of Oxygen which is 

 requisite for its vital actions (especially for those of the JS T ervo-Muscular 

 apparatus) ; and at the same time to carry off the particles which are set 

 free by the disintegration or "waste" of the tissues, and which are to be 

 removed from the body by the Excreting processes. Of these processes, the 

 one most constantly in operation, as well as most necessary for the mainte- 

 nance of the purity of the blood, is the extrication of Carbonic Acid through 

 the Respiratory organs; and this is made subservient to the introduction of 

 Oxygen into the system. In Man, as in other Vertebrated animals, there 

 is a regular and continuous movement of the nutritive fluid through the 

 sanguiferous vessels; and upon the maintenance of this, the activity of all 

 parts of the organism is dependent. In common with Birds and Mammals, 

 again, Man has a Respiratory circulation entirely distinct from the Systemic ; 

 all the blood which has returned from the body being transmitted to the 

 lungs, and being brought back to the heart again, before it is sent forth 

 afresh for the nourishment of the tissues and for the maintenance of their 

 functional activity. The Heart is placed at the junction of these two dis- 

 tinct circulations, which maybe likened to the figure 8; and it may be 

 said to be formed by the fusion of two distinct organs, a " pulmonary " and 

 a "systemic" heart; for its right and left sides, which are respectively ap- 

 propriated to these purposes, have no direct communication with each other 

 (in the perfect adult condition, at least), and seem merely brought together 

 for economy of material. 2 Each system has its own set of Arteries or effer- 

 ent vessels, and of Veins or afferent trunks; these communicate at their 

 central extremity by the Heart, and at their peripheral extremity by the 

 Capillary vessels, which are nothing else than the minutest ramifications of 

 the two systems, inosculating into a plexus. Besides the systemic and pul- 

 monary circulations, however, there is another which is no less distinct, 

 although it has not an impelling organ of its own. This is the " portal " 

 circulation, which is interposed between the venous trunks of the abdominal 

 viscera and the Vena Cava, for the purpose of distributing that blood through 



1 On the subject of the latter portion of this section, see tin- treatise of Dr. Robert 

 Williams on Morbid Poisons, the Principles of Medicine of Dr. Charles J. 8 Wil- 

 liams, the Lectures on General Pathology, by Mr. Simon, and the chapter on Specific 

 J>i-e;ises in Mr. Panel's Lectures on Surgical Pathology, vol. i. 



2 At an early period of fu-tal life, as in the permanent state of the Pugong, the 

 heart is so deeply cleft, from the apex towards the base, as almost to give the idea of 

 two .-eparate organs. 



