872

THE BLOOD-HÆMATIN.

dependent upon the iron which it contains, since nearly the whole of this substance may be removed without affecting the dark brown colour of the hæmatin; for example, if hæmatin be allowed to remain for some time in contact with concentrated sulphuric acid, and the liquid be then diluted, an evolution of hydrogen will take place, and ferrous sulphate will be formed in the liquid. The insoluble residue thus obtained contains carbon, hydrogen, nitrogen, and oxygen, in the same proportion as in hæmatin from which the iron has not been removed. If chlorine be passed through a solution of hæmatin in water, ferric chloride is formed, and a white precipitate, termed chlorhæmatin, is produced, which Mulder represents as (HN24C112, or €44H4N ̧Ð ̧, 6 Ch1⁄2Ð ̧), a compound analogous to that which is formed with protein, when albumin, suspended in water, is similarly treated. Hæmatin constitutes but a small proportion of the red particles of the blood (according to Berzelius, about 1-20th), the remaining portion consisting chiefly of globulin.

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It is difficult to obtain hæmatin in a state of purity, and as yet it has only been insulated in its coagulated form. Blood which has been freed from fibrin by agitation with twigs before coagulation, is to be mixed with about 8 times its bulk of a saturated solution of sodic sulphate. After standing for a few hours, the colouring matter subsides; it must be collected on a filter, and washed with a solution of sodic sulphate. If the residue upon the filter be now boiled with alcohol acidulated with sulphuric acid, the colouring matter is dissolved. The liquid must be filtered while hot, and a portion of globulin, which has been dissolved, is to be thrown down by the addition of carbonate of ammonium. The red liquid thus obtained is again to be filtered, and evaporated to dryness; after which the solid residue must be digested successively with water, alcohol, and ether, and again be dissolved in alcohol containing ammonia, by which the remaining portions of globulin will be separated in the insoluble form; the solution is then to be filtered and evaporated to dryness; after which everything that is soluble is to be removed by digestion with water. The residue is considered to be pure hæmatin.

Coagulated hæmatin as thus obtained forms a dark mass, which assumes a slight lustre on pressure. It is destitute of odour and of taste, and is insoluble in water, alcohol, ether, and the fatty and essential oils. It is, however, readily dissolved by weak alcohol which has been acidulated with sulphuric or hydrochloric acid: the solution is of a deep brown colour, but it becomes blood red on the addition of an alkali. Water precipitates the acidulated

THE BLOOD-HÆMATOIDIN.

873

alcoholic solution. Strong acids decompose hæmatin, and extract the greater portion of its iron. Aqueous solutions of the alkalies, both caustic and carbonated, dissolve it freely; when these solutions are boiled, the colour, which is at first bright red, passes through dull red into green. Hæmatin is precipitated completely from its ammoniacal solution in alcohol, by salts of silver, of lead, and of copper. According to Denis, 1000 parts of blood contain 056 of metallic iron; so that reckoning the quantity of blood in a man of average stature at 30lb., it would amount to about 120 grains of iron in the blood of the entire human body.

(1683) Hæmatoidin.-A remarkable modification of the contents of the red globules of the blood of hæmato-globulin, to which the name of hæmatoidin or hæmato-crystallin has been given, has been observed to occur sometimes in old extravasations, and in certain forms of disease. The colouring matter assumes the shape of irregular crystalline fragments, or of perfectly-formed transparent red rhombic prisms, which are very sparingly soluble in water; yielding a solution which becomes coagulated at about 145°. Alcohol and nitric acid also produce a precipitate in the liquid. The aqueous solution of hæmatoidin is precipitated by solutions of corrosive sublimate, of mercurous nitrate, and of cupric sulphate. Acetic acid dissolves the crystals of hæmatoidin readily; ammonia produces a liquid of the colour of peachblossoms; potash does not dissolve them, but changes the colour of the crystals to a dirty yellow. If digested in the presence of chlorides, with a great excess of glacial acetic acid, the globulin is separated, and a crystalline body known as hæmin (hydrochlorate of hæmatin) is separated; and from this, by the addition of an alkali, the hæmatin may be obtained.

Lehmann has pointed out a method by which the crystals of hæmatoidin may be readily obtained from the blood of various animals, particularly from that of the guinea-pig, the rat, and the mouse. After the serum has been well drained from the clot, the coagulum is to be placed in a cloth, and the greater part of the colouring matter washed out by means of a small quantity of water. The deep red liquid thus obtained is to be filtered, and a current of oxygen gas transmitted through it for about half an hour after this, a current of carbonic anhydride is to be transmitted through the solution, for about 15 minutes. During the latter process the liquid gradually becomes filled with small crystals which, if allowed to subside, can be separated from the liquid portion. Lehmann found that the formation of these crystals was favoured by the action of solar light, but the exact

874

THE BLOOD-HÆMATO-GLOBULIN.

changes which attend their production are not understood. The crystals obtained from the blood of different animals present differences of form and of solubility. They are generally prismatic, but those of the rat and the mouse are tetrahedral, and are very sparingly soluble, requiring 600 parts of water for their solution. The ultimate analysis of hæmatoidin furnishes results almost identical with those obtained from albumin. The purified crystals from the blood of a dog contained from 07 to o'9 per cent. of ash, more than half of which consisted of ferric oxide; phosphates were also present in considerable proportion.

(1684) Hæmato-Globulin. - The globulin with which the hæmatin is combined has already been described (1653) as a compound bearing a strong analogy to albumin; it is contained in a state approaching to purity in the crystalline lens, and it constitutes the most abundant ingredient in the blood-globules.

The combination of globulin with hæmatin, or hæmato-globulin, which is present in the red corpuscles, is very readily acted upon by oxygen, and by many other gases, and is concerned intimately with the changes produced in the blood during the process of respiration. Oxygen gas is absorbed by the red corpuscles when suspended in the serum or when dissolved in water, the liquid assuming a brilliant red colour, whilst a disengagement of carbonic anhydride occurs. It is owing to this action of oxygen that in the coagulum of venous blood, the upper portion, which is the part most exposed to the action of the air, is of a brighter red than the lower portions of the clot. Carbonic anhydride is likewise absorbed by the red particles; their colour then becomes changed to a dull purple, but the brilliancy of the red hue may be restored by further exposure to the action of oxygen: many saline solutions, such as those of potassic nitrate, also restore the red colour, and a similar effect may be obtained if syrup be added to the liquid. The solution of the colouring matter in water also experiences similar modifications in colour. Sulphuretted hydrogen causes the colour to pass into a dull green, and the red hue cannot be afterwards restored. Nitrous oxide colours hæmato-globulin purple, and oxygen reproduces the scarlet colour in blood which has been thus acted upon. Sulphurous anhydride, and acid gases in general, darken its colour, which is again restored by oxygen. Admixture with saline solutions also restores the red hue to blood which has been darkened by sulphurous acid. From these facts it is obvious that hæmato-globulin is a compound extremely prone to change under the influence of many reagents.

(1685) 2. CHYLE.-The term chyle is applied to the liquid derived from the nutritive portions of the food, which are absorbed from the inner surface of the intestines by a set of vessels, termed the lacteals; these pour their contents into one large absorbent trunk, called the thoracic duct, by which the chyle, as fast as it is supplied, is emptied into the general current of the circulation. The chyle differs in its qualities according to the nature of the food which has been taken, and according to the situation in which it is collected for examination. When removed from the body, it, in the course of a few minutes, undergoes a spontaneous coagulation, owing to the presence of fibrin. In this respect chyle differs from all the other animal fluids, except blood and lymph.

Chyle is an opalescent fluid, of a yellowish-white, or pale reddish colour. It has a somewhat saline mawkish taste, and a very feebly alkaline reaction; it is generally more or less milky, from its holding in suspension minute granules, and globules of fatty matter; this milkiness is particularly observable when the food has contained much fat. Chyle, when boiled, generally deposits a few albuminous flocculi. Few satisfactory opportunities have occurred for examining the composition of human chyle. The proportion of fibrin contained in the chyle of the lower animals is subject to considerable fluctuations. In the chyle of a horse it was found by Simon to amount to 0'44 parts per cent. ; in that of a cat Nasse found 0.13 parts of fibrin; and Rees found 0'37 parts of fibrin per cent. in that of the ass. When collected from the lacteals, before passing through the mesenteric glands, chyle frequently does not coagulate spontaneously, and the coagulation only occurs fully in that taken from the thoracic duct.

It has been observed that the quantity of fibrin is greater in animals from which the chyle has been collected while fasting. The quantity of fibrin in the chyle is also increased after passing through the mesenteric glands, as though a considerable portion of fibrin were added during its transmission through these organs. It appears not to be improbable that the albuminous matters are gradually converted into fibrin during their passage through the vessels, in the same way that albumin is formed whilst the aliments are passing from the stomach through the small intestines; since the quantity of fibrin increases, the nearer it approaches to the point where the chyle empties itself into the general mass of the circulating fluid. A few blood corpuscles are found floating in the chyle when it has reached the thoracic duct; and, when viewed by the microscope, multitudes of minute granules are seen in suspension, in addition to which there are other corpuscles,

resembling those of pus in appearance; besides which floating globules of fat are discernible in considerable numbers: in fact, chyle resembles blood in composition, but it is far more dilute; the proportion of solid matters in the chyle of the horse varying from 4 to 9 per cent., whilst in the blood it rises as high as 22 per cent. Chyle usually contains a modification of albumin, which Prout termed incipient albumin, in quantity varying from 1 to 5 or 6 per cent., according as the food has contained a larger or smaller quantity of azotised matter. The chyle, on exposure to the air, assumes more or less of a red colour, and thus approximates in another remarkable particular to the blood. This colour becomes increased in intensity after the liquid has passed through the mesenteric glands.

(1686) 3. LYMPH.-This is a colourless, or yellowish fluid, which has usually a faintly alkaline reaction. It is procured from the lymphatic vessels, and, owing to the difficulty of obtaining it in sufficient quantity, it has been but imperfectly examined. It is distinguished from all other animal fluids, except the blood and the chyle, by the presence of fibrin in solution: in consequence of which it coagulates in a few minutes after it has been withdrawn from the body, and forms a scanty colourless coagulum. The quantity of fibrin in lymph from the human body, obtained in cases of injury, has been found to be between 0.3 and 0'5 per cent.; in the horse it varied from o'04 to 0'33 per cent. The quantity of albumin in human lymph is stated to vary from 04 to 60 per cent., but in the latter case it is not improbable that the lymph was mixed with effused serum.

(1687) 4. MILK.-This important secretion is produced by the mammary gland of the female animal of the order Mammalia, after giving birth to young from the circumstance that the milk constitutes the entire food of the young animal for many months, it presents a high degree of physiological interest in relation to the supply of food, and to the processes of nutrition and of growth.

Milk is a liquid of a well-known yellowish, or bluish-white appearance, which is produced by the presence of a large quantity of oily matter in suspension. It has a sweet taste, a slight but agreeable odour, and in woman and the herbivora it has a feebly alkaline reaction: in the carnivora it is slightly acid. When allowed to stand undisturbed for a few hours, the greater part of the fatty matter rises to the surface, and forms the layer which constitutes cream. When viewed by the microscope in a very thin layer, milk appears to be transparent: it contains a large