(g) Creatinine. Take 100 c.c. of urine: add 5 c.c. of a saturated solution of sodium acetate and 20 c.c. of a saturated solution of mercuric chloride. Filter. Set the filtrate aside for twenty-four hours, and a spherical mercury compound of creatinine crystallises out. Examine this with a microscope. For colour test with sodium nitro-prusside see p. 142. (a) Blood. Microscope (blood corpuscles). Spectroscope (for oxyhæmoglobin or methæmoglobin). Hæmin test. (b) Blood pigment may be present without blood corpuscles. Spectroscope. (c) Bile. Gmelin's test. Hay's sulphur test. (d) Pus. White deposit. Microscope (pus cells). Add potash; it becomes stringy. (e) Albumin. (i.) Precipitated, if acid, by boiling; precipitate insoluble in acetic acid, so distinguishing it from phosphates. (ii.) Precipitated by nitric acid in the cold. (iii.) Precipitated by picric acid. (f) Sugar. (i.) Brown colour with potash and heat (Moore's test). (ii.) Ferments with yeast. (iii.) Reduces Fehling's solution. (iv.) Urine has a high specific gravity. (v.) Add picric acid, potash, and boil; the urine becomes a dark opaque red; the similar slight coloration in normal urine is due to creatinine. (g) Acetone. For colour test see p. 168. (h) Mucus. Flocculent cloud; may be increased by acetic acid; soluble in alkalis. A little mucus in urine is not abnormal. (i) Deposits. i. Examine microscopically for blood corpuscles, pus cells, crystals, &c. ii. Phosphates. White deposit often mixed with mucus or pus. Insoluble on heating; soluble in acetic acid. Urine generally alkaline. Examine microscopically for coffin-lids of triple phosphate and star-like clusters of stellar (calcium) phosphate. iii. Urates. Pink deposit, usually amorphous; may be mixed with envelope crystals of calcium oxalate. Deposit soluble on heating urine. Murexide test. iv. Uric acid. Deposit like cayenne pepper. above. Microscope. Tests as ADVANCED COURSE INTRODUCTION It will be presupposed that students who take the following lessons have already been through the elementary course. The order in which the subjects are treated is the same as that already adopted. The instructions given will be mainly practical; theoretical matter on which they depend, or to which they lead, is, as a rule, too lengthy to be discussed in a short manual like the present volume. The Appendix contains a description of various instruments which are not generally contained in sufficient numbers in a physiological laboratory to admit of each student being able to use them in a class. It also contains a description of certain methods of research which should always be shown in demonstrations, though there may be practical difficulties in allowing each member of the class to perform the experiments. The few experiments in which living animals are employed will also necessarily be of the nature of demonstrations. LESSON XIII CARBOHYDRATES 1. Glycogen. A rabbit which has been fed five or six hours previously on carrots is killed by bleeding. The chest and abdomen are opened quickly and a cannula inserted into the portal vein, and another into the vena cava inferior. A stream of salt solution is then allowed to pass through the liver until it is uniformly pale. The washings are collected in three beakers labelled a, b, and c. The liver is cut out quickly, chopped into small pieces, and thrown into FIG. 55.-Hot-air oven with gas regulator (G). (Gscheidlen.) boiling water acidulated with acetic acid. The acidulated water extracts a small quantity of glycogen. The pieces of scalded liver are then ground up in a mortar with hot water, and thoroughly extracted with boiling water. Filter. A strong solution of glycogen is thus obtained. Test the solution when cold with iodine. To separate the glycogen evaporate the solution to a small bulk on the water-bath and then add excess of alcohol; the glycogen is precipitated as a flocculent powder, which is collected on a filter and dried in an oven at the temperature of 100° (see fig. 55). If the experiment is to be a quantitative one, the piece of liver taken and the glycogen obtained must be weighed.1 2. Examine the washings of the liver in the beakers a, b, and c for sugar. This may be done in a rough quantitative manner as follows:-Take equal This method of preparation of glycogen has the advantage that only traces of protein are mixed with it. In Külz's method (extraction with dilute potash) there is more protein. This is precipitated by the alternate addition of hydrochloric acid and potassio-mercuric iodide. Pavy and also Pflüger recommend extraction with strong potash, and subsequent precipitation with a certain percentage of alcohol; this method extracts all the glycogen easily. |