When the serum is examined more minutely, it is found to coagulate, when heated to the temperature of 150°, when it appears like dirty boiled white of egg. It therefore contains albumen; and modern chemistry has shown that it holds in solution gelatine, corbonatc of soda, muriate of soda, phosphate of soda, a little pure soda, phosphate of lime, and hydro-sulphuret of am monia.
The cruor of the blood consists principally of fibrine, but great part of it is soluble in water, and the solution contains subphosphate of iron, a little soda, and sonic al bumen.
The blood of the fce,tus differs in sonic respects from that contained in the vessels after birth. It is of a darker colour, contains no fibrine, and no phosphoric acid, but appears to contain a greater quantity of gela tine than ordinary blood. As the body increases, and as the person advances in age, the proportion of gela tine seems to diminish, while that of phosphoric acid and fibrine probably increases.
Such are the nature and properties of the blood in general, but the blood contained in one set of vessels has a very different colour from that in another set. The blood contained in the ramifications and trunks of the venir cavx, the pulmoitic sinus, pulmonic auricle, puh»onic ventricle, and the trunk and branches of the pulmonary artery, is of a dark red or crimson colour, while that contained within the branches and trunks of the pulmonary veins, in the systemic sinus, the syste mic auricle, the systemic ventricle, and the trunk and ramifications of the aorta, is of a florid red or scarlet colour. We shall not at present inquire on what this difference depends, but merely notice the fact, as it leads to an important conclusion respecting the propri ety of the nomenclature which we have adopted in de scribing the sanguiferous system. Blood of a dark or crimson colour is commonly called venous blood, and that which is of the florid or scarlet red, is called arte rial blood ; but as dark blood is contained in the pulmo nary artery, and florid blood in the pulmonary veins, that distinction is evidently improper, and ought to be abolished. We think that Dr Barclay has much im proved the nomenclature of the sanguiferous system, by denominating those parts of it which contain dark blood destined to be distributed to the lungs, Pubuonic ; and those which contain fiorid blf,e,d, destined to supply the system at large, 8y.vte uric'.
All the organs of circulation occasionally exhibit a varit ty of morbid appearances ; but these arc most re. markahle in the heart and pericardium. 'Hie pericar dium is sometimes inflamed, and pit ternatmal adhesions are lound to has(• taken place between and the heart. It is sometimes cartilaginous or bony, and syrofolous tumours nut unfrequ•ntly appear about it. ln a few cases the watery fluid within the pericardium is almost want ing, but more frequently its quantity is increased. Dr Baillic once saw a case in which the pericardium was entirely wanting.
The heart is sometimes found in a state of inflamma tion, and fibrous concretions, called bole/fa, are often seen w ithin its cal iti•s. In some cases the heart is unusually loaded with fat. A rupture is occasionally found to have taken place, either in the substance, or in the valves of the heart, and a preternatural dilatation, called aneurism, either in the cavities of the heart, or, what is more usual, in the arch of the aorta, is now and then observed. Parts of the sobstance of the heart, of its valves, of the aorta, or of the corona•) arteries, are olten found ossified or bony ; and still more frequently, sonic of these parts are found to be thickened and opaque, or whitish. That peculiar kind of worm called hudatid, is sometimes found within the heart. The sub stance of the heart has been found extremely soft, and sometimes of a scirrhous hardness.
The appearance of aneurismal swellings in the arte ries and enlargements in the \ e ins, called Vdri C'iSe SW( are not On the structure of the heart, arteries, and veins, See Winslow, Truitt, ; Senac, 'Traite du Caur ; Biehat, „lnutrimir Descriptive, tom, iv. and Grit, rule, tom. ii. ; Portal's Lours rale, tom. iii. ; Descriptio ..I•teria•uul Cor119 ris. flanzani ire Thoulas reducta ; or two translations of the same work, one by i\lr Archibald Scott, published at Edinburgh, and another at London, under the aus pices of 'Mr James Alacartney ; Bell's ?2/atomy, vol. ii.; and Fy Compendium of .100tom1/, vols. ii. and iii. For figures illustrating the distribution of the arteries, Sec Haller's Icom.s Anatomicx ; Loder's Tabula' ; and I\ 1r Charles Bell's of the .1rtcricu.