through the mesenteric glands and thoracic duct, and is eventually poured into the general current of the circulation near the junction of the left internal jugular and subclavian veins. In this manner the blood is constantly receiving fresh material derived directly from the intestinal canal.

If examined during the progress of digestion, chyle is a white creamy fluid of slight alkaline reaction, rich in oil globules, and, like blood, separates into clot and serum; the coagulum forming a bulky soft gelatinous clot which after exposure to the air acquires a rosy tint. The serum is turbid, and contains albumin and salts in solution; it is coagulated by heat and acetic acid.

The chyle derived from the intestinal lacteals does not contain fibrin, and consequently does not separate into clot and serum.

If the animal has been fasting, the chyle loses creamy appearance and becomes more transparent and of a yellowish colour.

1 Analysis by author, "Case of Chyluria,” in Pathological

Society's Transactions, 1878.

The albuminous matters consist of albumin, casein, fibrin; and the peptones, as is evidenced by the readiness with which chyle passes through a filter of parchment paper.

The fatty matters consist of minute spherical globules, and form the molecular base of the chyle: their diameter is estimated at of an inch, they disappear on the addition of ether.

Among the extractives, urea tyrosin (§ 30), and sugar (§ 3), obtained.

(§ 35), leucin (§ 29), have been frequently

The ash much resembles that of blood; the sodium having a preponderance over the potassium salts, and the phosphates over the chlorides. For the separation of the above the student should proceed in the manner as directed in the examination of blood.

(56) LYMPH is a clear, colourless, or strawcoloured transparent fluid, of alkaline reaction and saline taste; it is obtained from the lymphatic vessels and glands. In composition lymph closely resembles chyle, differing chiefly in the smaller proportion of fibrin and fatty matter it contains.

*(57) Pus is a pathological fluid, and consists essentially of a liquid portion, "liquor puris,” which is exuded liquor sanguinis, and white corpuscles or

leucocytes, which cannot be distinguished from the white corpuscles of the blood.

I. THE PUS CORPUSCLES can be separated from the liquor puris by the addition of a 10 per cent. solution of sodium chloride, and the precipitated mass removed by filtration and thoroughly washed with the same solution till quite free from serum. The pus corpuscles or leucocytes are spherical, irregular bodies about 0 to 3500 of an inch in diameter, containing a number of granules and one or more nuclei.

(a) Treated with dilute acetic acid, they swell up and become more transparent and the nuclei more distinct.

(b) Treated with ammonia or potash solutions, pus becomes tenacious and jelly-like; this character distinguishes it from mucus, which becomes less tenacious and more fluid in the addition of these solutions.

2. ALBUMINS.

(a) An albumin coagulable at the ordinary temperature of sero albumin, 70° C.

(c) Alkali albuminate or casein, precipitated by

acetic acid.

(8) An albumin insoluble in water, soluble in hydrochloric acid, swelling up in solution of sodium chloride (Rovida's hyalin substance).

1 The proportion of solids to the water varies of course with the nature of the pus formed; thus, in ichorous, muco- or seiopus, the solids are diminished.

3. THE EXTRACTIVES contain urea (§ 35); leucin (§ 29); cerebrin (§ 59, p. 99); lecithin (§ 59, p. 100), and Sugar (§3).

4. The SALTS consist chiefly of sodium, potassium, and calcium phosphates, and carbonates with traces of iron and magnesia. Pus formed in the soft tissues contains often only a trace of calcium phosphate, but pus derived from the neighbourhood of diseased bones often contains 2.5 per cent. (For quantitative estimation, proceed as directed for estimation of salts in blood.)

Requirements for Demonstration VI.

MATERIALS.-Fresh bullock's blood, collected in deep and shallow vessels. Whipped fibrin from freshly flowing blood. (N.B. Both these can be obtained from the slaughter-house.) Blood of rat or guinea-pig for hæmoglobin. Milk.

REAGENTS.-Alcohol; ether; calcium carbonate; magnesium sulphate; sodium chloride; hydrogen peroxide. Solutions of ammonia, ammonium sulphide, ammonium ferrous sulphide with tartaric acid; alkaline cupric sulphate (Fehling's solution); magnesium sulphate; potassium hydrate; sodium chloride (10 per cent.). Acids: acetic, nitric, sulphuric, hydrochloric.

APPARATUS.-Small glass flask; pipette; spectroscope; carbonic acid gas generator; beakers; test-tubes; stirring-rods; glass slides; filters; filter-paper; red and blue litmus paper.

DEMONSTRATION VII.

SOLID TISSUES.

(58) MUSCLE. The tissue of voluntary muscle consists of a number of delicate tubes or fibrillæ, formed by a sheath of sarcolemma containing a semi-fluid plasma, with nuclei mixed up with elements of connective, adipose, vascular, and nervous tissues. The sarcolemma resembles elastic tissue in its chemical characters it does not yield gelatin by boiling, nor is its elasticity affected by the action of acids and alkalis. The gelatin which is obtained from muscular tissue is therefore not derived from the sarcolemma, but from the connective tissue which binds the muscular fibrils together.

The muscular plasma is obtained by injecting the muscles of a freshly killed animal with a 1 per cent. solution of sodium chloride; and when the blood is thoroughly washed out, the muscles are cut up into minute fragments, frozen, and mixed with four times their volume of snow containing 1 per cent. of sodium chloride; at 0° C. the mass becomes liquid, and must