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It will be found that the following method of destroying organic matter is far better than incineration: evaporate to dryness, and then heat with fuming nitric acid for some hours in a water-bath, adding more acid from time to time till all effervescence ceases. Finally evaporate to dryness: the saline matters only are present in the residue.

Pribram and Gerlach have shown that calcium, magnesium, phosphoric acid, and sulphuric acid may be precipitated from serum by the same methods as in aqueous solutions. The precipitates are collected by centrifugalising, and then washed by decantation. This method of direct precipitation also avoids all those sources of error that result from the process of ignition.

The physiological importance of the inorganic constituents of the blood.—It is well known that distilled water acts like a poison to protoplasm; fishes kept in it die quickly, cilia stop moving, white blood corpuscles burst. Thus in physiological research one commonly uses a 0.6 per cent. solution of sodium chloride in order to keep muscles, nerves, &c., moist during an experiment. Dr. Ringer' has shown, by a large number of observations on fish, tadpoles, cilia, skeletal muscle, but more especially in connection with the heart, the relative importance and action of the different salts of the blood. Minute quantities of such salts, such as occur, for instance, in river water, are quite sufficient to keep fish alive for weeks, which would die in distilled water in a few hours. Kronecker and his pupils maintain that the frog's heart does not feed on its own substance, but that as soon as nutritive fluid is withdrawn its contractions stop. They state that fluids only, which contain serum-albumin will sustain the heart's contractility. They showed that a 0-6 per cent. solution of sodium chloride soon stops the heart, and so it undoubtedly does. Merunowicz,3 however, finds that the dissolved ash of incinerated blood supports the heart's contractility, and Ringer has shown that a good circulating fluid for the heart may be compounded by mixing small quantities of such salts as nominally occur in the blood, and that with this fluid the heart after removal will continue to beat normally as long, or nearly as long, as it does with defibrinated blood. The necessity for lime salts is especially great; in fact the close adhesion of proteids generally with small quantities of mineral matter is rather suggestive of combination than mere mixture. Lime salts adhere especially closely, and, in fact, seem indispensable for many of the functions of the body, of which the beating of the heart and the contraction of skeletal muscle are good examples. Blood from which the salts have been removed by dialysis keeps the heart going, but the tracing is abnormal, resembling that produced by a weak solution of a lime salt; it is in fact found that dialysis will not remove the lime from serum-albumin, though it removes the greater part of the sodium and potassium salts. Saline solutions like Ringer's circulating fluid contain salts of all three metals; they have been employed for transfusing into the blood vessels of persons who have suffered severely from hæmorrhage. The following is the composition of Ringer's circulating fluid :

100 c.c. of a 0.75 per cent. solution of sodium chloride.

1 c.c. of a 10 per cent. solution of calcium chloride.

1 c.c. of a 0.75 per cent. solution of potassium chloride.

1 c.c. of a 10 per cent. solution of bicarbonate of soda.

1 S. Ringer, Journ. of Physiol. iii. 380; iv. 29, 222; v. 98; vi. 361; vii. 118, 291; viii. 15, 20, 288; xi. 79.

2 Martius, Du Bois Reymond's Archiv, 1881, p. 474. Kronecker and Von Ott, Ibid. p. 569. Martius, Ibid. 1882.

5 Arbeiten aus der physiologischen Anstalt zu Leipzig.

The following has, however, been more recently proved by Ringer to act even better than the above :—

100 c.c. of a 0-75 per cent. solution of sodium chloride

saturated with calcium phosphate

1 c.c. of a 20 per cent. solution of potassium chloride.

Ludwig's circulating fluid contains a trace of commercial peptone in addition to inorganic constituents. Its composition is as follows:

100 c.c. of water

0.5 gram of sodium chloride

0-002 gr. of potassium hydrate
0-003 gr. of peptone.

(The commercial peptone contains the necessary lime salts.)

THE WHITE BLOOD CORPUSCLES OR LEUCOCYTES The white blood corpuscles are typical animal cells; they consist of more or less granular masses of protoplasm, containing a nucleus in the centre. Their protoplasm exhibits movements, which are termed amoeboid, from their resemblance to the movements of the amoeba. Amoeboid movement was first observed in white blood corpuscles by Wharton Jones. These movements can be most readily observed with the microscope, while using a warm stage the temperature of which is about 40°C. It is by virtue of such movements that locomotion becomes possible to these corpuscles; this may lead to their emigration from the blood vessels, and when in the tissues, they are termed wander-cells. Emigration takes place to a much greater extent than normal in inflamed parts, and may go to such an extent as to cause the formation of an abscess, i.e. a collection of pus or white blood corpuscles suspended in a fluid like serum in composition.

It is in virtue of their amoeboid movements, and power of assimilation, that white blood corpuscles are enabled to take up nutritive substances from the lining membrane of the alimentary canal. Fat globules for instance can be readily seen in these corpuscles at a certain stage during absorption.

White blood corpuscles also disintegrate readily; the changes which occur in them when the blood is shed have been already referred to (p. 240). They also probably disintegrate in the lacteals or lymphatic vessels of the intestine; and in so doing, liberate the nutritious substances derived from the alimentary canal.

White blood corpuscles are not nearly so numerous in the blood as are the red. Their number varies with age, sex, period after food and region from which the specimen of the blood is taken. On an average in man there is one white corpuscle to every 350 red ones, i.e.

1 Wharton Jones, Phil. Trans. 1846.

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about 15,000 in every cubic millimetre of blood. They are not constant in size, but in man they average about 0·01 millimetre (inch) in diameter; they are somewhat larger in the lower vertebrate groups. They are always found in greater abundance on the upper surface of a blood clot than in the lower part, a fact which shows that their specific gravity is less than that of the red corpuscles.

White blood corpuscles are however found not only in the blood stream; they are also found in lymphatic vessels, where they are called lymph cells; some of the lymph cells are no doubt emigrated white blood corpuscles, but most of them are derived from lymphatic glands. The lymphatic glands are collections of lymph cells contained in a meshwork of a variety of connective tissue, called retiform tissue. It is here in fact that the lymph cells are formed from the subdivision of previously existing cells. When fully formed they work their way by means of their amoeboid movements into the path of the lymph stream as it goes through the lymphatic glands. Lymphoid or adenoid tissue, i.e. tissue similar to that found in lymphatic glands, exists in many other parts, e.g. the thymus and tonsils, the solitary glands and agminated glands of the intestine, and the Malpighian corpuscles of the spleen; it forms the greater part of the corium of some mucous membranes; and it is found in microscopic patches in the lungs, liver, and other

organs.

Microchemical research is obviously the only method of chemical research open when one wishes to investigate the white corpuscles in the blood. For macrochemical methods one has to obtain a supply of lymph cells from structures like lymphatic glands or the thymus; or one may use pus. In pus, however, the corpuscles cannot be regarded as normal, and have undergone certain retrogressive changes. It seems, however, quite legitimate to suppose that the white corpuscles, which are in origin lymph cells, resemble them in their chemical properties.' It will be convenient to take the nucleus of these corpuscles first, and then to consider the cell body or protoplasm.

The nucleus. Like the nuclei of cells generally, the nucleus of the white corpuscle can be demonstrated to consist of a network which stains readily, and which is called chromatin, and an achromatic substance (i.e. a substance that is not easily stained by staining reagents) which has also been called nucleo-hyaloplasm (Strasburger) and para-linin (Schwarz). These and similar terms, however, which

1 Wooldridge in his Arris and Gale lectures (Blood-plasma as Protoplasm, Roy. Coll. of Surgeons, 1886) pointed out certain differences between lymph cells and white blood corpuscles, in their influence upon coagulation. Such differences do not, however, affect the present argument.

have been already more fully explained (p. 197), have more of a morphological than a chemical significance, and do not pretend to denote the chemical characters of the substances.

The complicated manner in which the component parts of the nucleus behave to microchemical reagents must mean that the nucleus is of a complicated chemical nature, and doubtless contains many important and distinct substances.

The chief chemical substance in the nucleus of which we have other than a microscopical knowledge is nuclein. Miescher's1 nuclein is considered by Zacharias to be identical with Flemming's chromatin.

Nuclein belongs to the heterogeneous group of substances called albuminoids, i.e. substances which are not proteids, but which resemble proteids in many points. Its physical characters are like those of mucin; in containing a high percentage of phosphorus, it however differs from mucin very markedly. Its insolubility in artificial gastric juice enables us to obtain it free from the investing protoplasm of the cells. Nuclein has been obtained from many varieties of cells, from spermatozoa, from yolk of egg, milk, and also from certain plant tissues. From the discrepancies in the published analyses of these substances (by Hoppe-Seyler, Miescher, Worm- Müller, Lubavin), it seems either that no definite chemical unit nuclein exists, or that the nucleins are a numerous class of organic phosphorus compounds; this latter conclusion seems to harmonise better with the results of microchemical investigation. The investigations of Kossel,3 in which he has shown distinct chemical differences in various kinds of Luclein, bear out this same view of the case (see p. 203).

The cell protoplasm.-Here again microscopic methods teach us that protopiasm is not always the uniform jelly we were once led to suppose, but consists in many cases of a fine network or reticulum, enclosing in its meshes a more fluid material or enchylema (Carnoy). In the white blood corpuscles the granules seem to be entangled with the reticulum.

On the application of dilute acetic acid, the granules and reticulum shrink around the nucleus. On the application of water, or more quickly with dilute potash, the protoplasm swells, and ultimately the corpuscle bursts and disintegrates. The partial disappearance of the granules when the blood is shed was observed by Haycraft to accompany the shedding out of the fibrin-ferment, or rather the formation of fibrin in the surrounding plasma.

By the use of osmic acid, fat granules, which are stained black by

1 Miescher, Hoppe-Seyler's Med. Chem. Untersuch. Heft iv. 441.

2 Botan. Zeitung, 1887.

5 Kossel, Zeitsch. f. physiol. Chem. x. 248.

this reagent, can be demonstrated to exist in the cell-protoplasm, but in especial abundance in the white corpuscles and lymph cells of the intestinal vessels during absorption. The same is true with regard to glycogen, which can be detected microchemically by a solution of iodine in potassium iodide; this stains glycogen a deep mahogany colour.

Lecithin, cholesterin, and inorganic matter exist in small quantities in the white corpuscles, but the bulk of the protoplasm is undoubtedly proteid in nature; and though our present methods do not enable us to say which proteids are contained in the reticulum, and which in the enchylema, yet by using extracts of lymph cells from lymphatic glands we can at least identify the proteids which are present. They are as

follows:

1. A mucin-like proteid similar to that described by Miescher2 in pus, and called hyaline substance by Rovida. This swells up into a jelly-like substance when mixed with 5 to 10 per cent. solutions of sodium chloride or magnesium sulphate; on pouring such a mixture into water, this proteid extends in cohesive strings through the water, which soon contract and float on the top. This substance is, however, not mucin, as it yields no reducing sugar on boiling it with sulphuric acid. It is also not nuclein, as the nuclei are not affected by the reagents used; it resembles globulins in its solubilities; it yields an ash rich in phosphorus ; and on digestion with artificial gastric juice an insoluble residue of the nature of nuclein separates out. In all these points this proteid resembles the class of proteids named nucleoalbumins' by Hammarsten.3 This is the most abundant of the proteids present in the protoplasm. It is probably identical with Reinke's plastin (see p. 205).

2. Two globulins. These are obtained by dissolving the proteids of the lymph cells in a liquid prepared by mixing a saturated solution of sodium sulphate with nine times its volume of distilled water. This solution does not cause the swelling up of the nucleo-albumin like sodium chloride or magnesium sulphate solutions do. Then on saturating this extract with magnesium sulphate a precipitate is obtained. This precipitate consists of the globulins, which may be washed, redissolved, and then separated by fractional heat-coagulation. They may be called cell-globulin a, which coagulates at about 50° C.; and cell-globulin, which coagulates at 73° C. On filtering off the heatcoagulum of cell-globulin a, which is generally only present in small quantities, the cell-globulin proper is alone left in solution, and this

1 Reports of the British Association, 1887, p. 145, and 1888, p. 363. Report of a Committee appointed to investigate the Physiology of the Lymphatic System. * Miescher, Hoppe-Seyler's Med. Chem. Untersuch. P. 441. 3 Hammarsten, Zeitsch. f. physiol. Chem. xii. 163.

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