Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/501

RESPIRATION 483 along. They have a diameter of ^rV^ inch when at rest and globular. They are far less numerous than the red corpuscles ; the proportion of white and red corpuscles in various conditions is shown in the following table : In the morning fasting state 1:716 Half an hour after breakfast V ....1 : 347 Three hours after breakfast 1 : 1514 In the splenic vein 1 : 60 In the splenic artery 1 : 2260 In the hepatic vein 1 : 170 In the portal vein 1 :740 In addition to typical white and red corpuscles there are others, provisionally called intermediate corpuscles, red granular corpuscles, or hsematoblasts, which are granular and nucleated. Probably these corpuscles are involved in a special manner in the development of the fibrin-ferment. It has been calculated that one cubic millimetre (i.e., a cube whose side measures about ^ T inch) contains five million corpuscles of all kinds. The chief constituents of the blood may now be dis- cussed seriatim : Constituents of the Liquor Sanguinis. Fibrin. When fresh this is an elastic substance belonging to the group of proteid bodies ; it is insoluble in pure water, but A B C D FIG. 8. Blood corpuscles. A, Moderately magnified; red corpuscles in roul- eaux ; white corpuscles at a, a. B, C, J), Red corpuscles more highly magnified. E, Red corpuscle swollen to a sphere by imbibition of water. F, While corpuscle, magnified same as B; G, the same, throwing out blunt processes ; K, the same, treated with acetic acid, and showing nucleus magnified same as D. If, J, Red corpuscles puckered or crenate //, all over, I, at edge only. (From Huxley's Elementary Physiology.) is soluble in solutions of common salt and in dilute hydrochloric acid at the temperature of the body. Human venous blood yields from 2 '2 to 2 '8 parts per thousand of fibrin. So far as we know, fibrin does not exist as such in the plasma before it is coagu- lated; but there does exist a body, fibrinogen, which is the precursor of fibrin. It may be separated from plasma by diluting the plasma freely with water at an ice-cold tempera- ture, and passing for a long time a stream of C0 3 through it ; or by adding common salt to plasma until the plasma contains 12 to 16 per cent, of salt posed that fibrin arises in the union of the two bodies fibrinogen and para-globulin. Serum-albumin. This is a proteid body which coagulates on heating. Certain extractive matters. These include neutral fats, lecithin, and cholesterin ; sugar ; urea, uric acid, creatine, creatinine, &c. ; and a yellow pigment. Inorganic Salts. These are the chlorides, phosphates, and sulphates of sodium, potassium, calcium, and magnesium ; sodium and chlorides are the main constituents. Gases. Especially C0 2 "; but see below. Constituents of the Red Corpuscles. Ozy haemoglobin. This interesting substance has the general chemical composition of an albuminous body with the addition oi the element iron: C, 54'00; H, 7'25; N, 16'25; Fe, 0'42; S, 0-63; 0, 21-45 = 100-00. It is the cause of the red colour of the corpuscles. It may be obtained in the form of beautiful crystals by a variety of methods, which all have the following steps in common : (1) to effect the solution of the oxy- hsemoglobin of the red corpuscles in the serum or in water, and (2) to effect the crystallization of it from solution either by adding alcohol, or by cold, or by both combined. The forms of the crystals differ in different animals ; the chief forms are given in fig. 9. Oxy- hsemoglobin has the property of giving up a portion of its oxygen on very slight provocation, e.g., when treated with easily oxidizable sub- stances, or when sub- mitted to moderate heat in a vacuum. The resulting sub- stance is called re- duced haemoglobin or, shortly, hsemo- globin ; it is capable of reproducing the original oxyhajmo- globin on simple ex- posure to oxygen or Fm- 9 ._Crystals of oxyhtemoglobin ; a, 6, <-, e, to air. This property forms from blood of man and majority of mammals : is of the highest im- d > tetraliedral crystals from blood of guinea-pig; /, portance in the func- hexa g nal crystals from squirrel blood, tion of respiration, as will be explained in the section on the gases of the blood. Solutions of oxyhsemoglobin of moderate strength have the fine scarlet hue of arterial blood. When interposed between the sun and a spectroscope they cause the absorption of definite portions E t> F G H FIG. 10. 1, 2, Spectra of solutions, 1 containing less than 0-01 per cent, and 2 containing 0-37 per cent, of oxyhsemoglobin ; 3, spectrum of solution containing about 0-2 per cent, of haemoglobin. the fibrinogen is precipitated in a flaky form. Besides fibrinogen, liquor sanguinis contains another proteid body intimately concerned in the formation of fibrin ; this is serum-globulin or para-globulin. It also may be precipitated from diluted plasma by a stream of C0 2 ; but it may be much more perfectly eliminated by adding magnesium sulphate until the plasma is saturated. It is a body the presence of which greatly facilitates or promotes the develop- ment of fibrin from fibrinogen ; indeed some observers have sup- of the spectrum, and give a characteristic appearance to it. After the solution has been reduced (as it may be very readily by means of an alkaline solution of a ferrous salt, in which precipitation of ferrous hydrate is prevented by the presence of tartaric or citric acid), it assumes a brownish colour and the absorption spectrum becomes changed. The spectra of oxyhsemoglobin and of reduced haemoglobin when the solutions are of moderate strength are given in fig. 10.