Gases. Oxygen, nitrogen, and carbonic acid exist in varying proportions. BLOOD CORPUSCLES. The corpuscular elements of the blood occur under two distinct forms, which from their color are known as the red and white corpuscles. The Red Corpuscles, as they float in a thin layer of the Liquor Sanguinis, are of a pale straw color; it is only when aggregated in masses that they assume the bright red color. In form they are circular and biconcave; they have an average diameter of the of an inch. In mammals, birds, reptiles, amphibia and fish the corpuscles vary in size and number, gradually becoming larger and less numerous as the scale of animal life is descended, e. g. :— TABLE SHOWING COMPARATIVE DIAMETER OF RED CORPUSCLES. Mammals. Man, Dog, Birds. 3200. Eagle, 1. Chimpanzee, 3417. Owl, 1783 Ourang, 3393. Sparrow, Lizard, T. 3542. Swallow, 13. Viper, 17. Siren, Reptiles. Amphibia. Fish. Turtle, 11 Frog, Trog. Perch, 2009. Tortoise, 1. Toad, Proteus, Amphiuma, 83. In man and the mammals the red corpuscles present neither a nucleus. nor a cell wall, and are universally of a small size. They can be readily distinguished from the corpuscles of birds, reptiles and fish, in which they are larger, oval in shape and possess a well-defined nucleus. The red corpuscles are exceedingly numerous, amounting to about 5,000,000 in a cubic millimetre of blood. In structure they consist of a firm, elastic, colorless framework, the stroma, in the meshes of which is entangled the coloring matter, the hæmoglobin. Hæmoglobin, the coloring matter of the corpuscles, is an albuminous compound, composed of C. O. H. N. S. and iron. It may exist either in an amorphous or crystalline form. When deprived of all its oxygen, except the quantity entering into its intimate composition, the hæmoglobin becomes darker in color, somewhat purple in hue, and is known as reduced hæmoglobin. When exposed to the action of oxygen, it again absorbs a definite amount and becomes scarlet in color, and is known as oxy-hæmoglobin. The amount of oxygen absorbed is 1.76 c.cm. (17 cubic inch) for I milligramme (grain) of hæmoglobin. It is this substance which gives the color to the venous and arterial blood. As the venous blood passes through the capillaries of the lungs, the reduced hæmoglobin absorbs the oxygen from the pulmonary air and becomes oxy-hæmoglobin, scarlet in color, and the blood becomes arterial. When the arterial blood passes into the systemic capillaries, the oxygen is absorbed by the tissues, the hæmoglobin becomes reduced, purple in color, and the blood becomes venous. A dilute solution of oxy-hæmoglobin gives two absorption bands between the lines D and E of the solar spectrum. Reduced hæmoglobin gives but one absorption band, occupying the space existing between the two bands of the oxy-hæmoglobin spectrum. The Function of the red corpuscles is, therefore, to absorb oxygen and carry it to the tissues; the smaller the corpuscles, and the greater the number, the greater is the quantity of oxygen absorbed; and, consequently, all the vital functions of the body become more active. The White Corpuscles are far less numerous than the red, the proportion being, on an average, about I white to 350 or 400 red; they are globular in shape, and measure the of an inch in diameter, and consist of a soft, granular, colorless substance, containing several nuclei. The white corpuscles possess the power of spontaneous movement, alternately contracting and expanding, throwing out processes of their substance and quickly withdrawing them, thus changing their shape from moment to moment. These movements resemble those of the amoeba, and for this reason are termed amaboid. They also possess the capability of moving from place to place. In the interior of the vessels they adhere to the inner surface, while the red corpuscles move through the centre of the stream. The white corpuscles are identical with the leucocytes, and are found in milk, lymph, chyle and other fluids. Origin of Corpuscles. The red corpuscles take their origin from the mesoblastic cells in the vascular area of the developing embryo. In the adult they are produced from colorless nucleated corpuscles resembling the white corpuscles. The spleen is the organ in which they are finally destroyed. The white corpuscles originate from the leucocytes of the adenoid tissue, and subsequently give rise to the red corpuscles and partly to new tissues that result from inflammatory action. COAGULATION OF THE BLOOD. When blood is withdrawn from the body and allowed to remain at rest, it becomes somewhat thick and viscid in from three to five minutes; this viscidity gradually increases until the entire volume of blood assumes a jelly-like consistence, which occupies from five to fifteen minutes. As soon as coagulation is completed, a second process begins, which consists in the contraction of the coagulum and the oozing of a clear, straw-colored liquid, the serum, which gradually increases in quantity as the clot diminishes in size, by contraction, until the separation is completed, which occupies from 12 to 24 hours. The changes in the blood are as follows:- The serum, therefore, differs from the Liquor Sanguinis in not containing fibrin. In from 12 to 24 hours the upper surface of the clot presents a grayish appearance, the buffy coat, which is due to the rapid sinking of the red corpuscles beneath the surface, permitting the fibrin to coagulate without them, which then assumes a grayish-yellow tint. Inasmuch as the white corpuscles possess a lighter specific gravity than the red, they do not sink so rapidly, and becoming entangled in the fibrin, assist in forming the buffy coat. Continued contraction gives a cupped appearance to the surface of the clot. Inflammatory states of the blood produce a marked increase in the buffed and cupped condition, on account of the aggregation of the corpuscles and their tendency to rapid sinking. Nature of Coagulation. Coagulated fibrin does not pre-exist in the blood, but is formed at the moment blood is withdrawn from the vessels. According to Denis, a liquid substance, plasmine, exists in the blood, which, when withdrawn from the circulation, decomposes into fibrin and met-albumen. According to Schmidt, fibrin results from the union of fibrinoplastin (paraglobulin) and fibrinogen, brought about by the presence of a third substance, the fibrin ferment. According to Hammersten and others, the fibrin obtained from the blood after coagulation, comes from the fibrinogen alone, the conversion being brought about by the presence of a ferment substance. Paraglobulin in this case having nothing to do with the change. This view is supported by the fact that the quantity of fibrin obtained from the blood is never greater than the quantity of fibrinogen previously present. The origin of the ferment is obscure, but there is reason to believe that it comes from the injured vascular coats or from the breaking up of the white corpuscles. Conditions Influencing Coagulation. The process is retarded by cold, retention within living vessels, neutral salts in excess, inflammatory conditions of the system, imperfect aeration, exclusion from air, etc. It is hastened by a temperature of 100° F., contact with air, rough sufaces and rest. Blood coagulates in the body after the arrest of the circulation in the course of 12 to 24 hours; local arrest of the circulation, from compression or a ligature, will cause coagulation, thus preventing hemorrhages from wounded vessels. The Composition of the Blood varies in different portions of the body. The arterial differs from the venous, in being more coagulable, in containing more oxygen and less carbonic acid, in having a bright scarlet color, from the union of oxygen with hemoglobin; the purple hue of venous blood results from the deoxidation of the coloring matter. The blood of the portal vein differs in constitution, according to different stages of the digestive process; during digestion it is richer in water, albuminous matter and sugar; occasionally it contains fat; corpuscles are diminished, and there is an absence of biliary substances. The blood of the hepatic vein contains a larger proportion of red and white corpuscles; the sugar is augmented, while albumen, fat and fibrin are diminished. Pathological conditions of the Blood. 1. Plethora-increase in the volume or quantity of blood. 2. Anæmia-deficiency of red globules with increase of water. 3. Leucocythemia-increase of white and diminution of red corpuscles. 4. Glycohemia-excess of sugar in the blood. 5. Uræmia-increase in the amount of urea. 6. Cholesteræmia-an excess of cholesterine in the blood. 7. Thrombosis and embolism-clotting of blood in the vessels and dissemination of coagula. 8. Lipamia-an excess of fat. 9. Melanæmia-pigment in the blood. CIRCULATION OF THE BLOOD. The Object of the Circulation is to distribute nutritious blood to all portions of the system and to carry waste materials to the various eliminating organs. The Circulatory Apparatus consists of the heart, arteries, capillaries and veins. The Heart is a hollow, muscular organ, pyramidal in shape, measuring 51⁄2 inches in length and weighing from 10 to 12 oz. in the male, and 8 to 10 oz. in the female. It is invested externally by a closed fibro-serous sac, the pericardium, containing a small amount of fluid, which prevents friction as the visceral and parietal layers glide over each other, during the movements of the heart and lungs. The heart consists of four cavities, a right auricle and ventricle, and a left auricle and ventricle, completely separated by a vertical partition. The right is the venous side, receiving the blood from the venæ cavæ, and propelling it through the pulmonary artery into the lungs; the left is the arterial side, receiving the arterial blood from the lungs by the pulmonary veins, and propelling it through the aorta to the system at large. The Auriculo-ventricular orifices are guarded on the right and left sides by the tricuspid and mitral valves respectively, while they are so arranged as to permit the flow of blood in the forward direction only; the orifices of the pulmonary artery and aorta are guarded by the semi-lunar valves. The Endocardium is a delicate, shining membrane, lining the interior of the heart, and continuous with the lining membrane of the blood vessels. The walls of the left ventricle are nearly half an inch in diameter, being |