account of the urine being retained after injury to the spinal cord. Prof. Harrison demonstrated elastic tissue below in the situation of the uvula and muscular fibres in other directions. The internal muscular coat is reticulated, and when hypertrophied, comes to resemble closely the columnar surface of the heart, especially the apicial bands, according to Mr. Ledwich. The mucous membrane of the bladder is pale, loose, and rugous, save at the "trigone," where it is smooth, fixed, and vascular. The Male Urethra has walls undoubtedly muscular, Hancock having traced that tissue from the longitudinal fibres of the bladder. They may give rise to spasmodic stricture, especially in the membranous portion, where two layers lie close to the mucous coat. Here, too, can be demonstrated striped fibres, constituting "Wilson's muscle," which Mr. Ledwich has always succeeded in finding, and "Guthrie's muscle," which is not so constant. The lodgment of the last few drops of water is prevented by the action of the accelerator urinæ. QUESTIONS FOR EXAMINATION. JUNIOR. 1. Define secretion, and say what chemical substances are removed by the process. 2. Describe the structure of the mammary gland, and compare it with the testis. 3. Sketch the circulation of the foetal liver. 4. What are the contents of a "portal canal?" 5. Give the chemical composition and uses of the bile. 6. Describe that part of the renal vessels where it is supposed the water of the urine escapes. SENIOR. 1. What are the respective influences of cerebro-spinal and sympathetic nerves on secretion? 2. Give the composition of milk, noting the differences presented at various periods, and by that of the cow. 3. Describe the minute anatomy of the liver, mentioning the opinions held as to the position of the hepatic cells. 4. Sketch the functions of the liver, including that discovered by Bernard. 5. Describe Mr. Richardson's method of preparing injections of the renal vessels. 6. What are the supposed sources and uses of the straight vessels of the kidney? THE URINE Is a clear, pale yellow liquid, with a saline taste and a peculiar aromatic odour when first passed, or in a much stronger degree when a drop of it is heated on platina foil. Its reaction is slightly acid, which, as well as colour and smell, is due to the urophæin, according to Heller. The more concentrated the urine the greater the acidity, colour, and smell. Others assign the acid reaction to lactic acid, and Liebig to acid phosphate, which view is supported by its being much less acid, or even alkaline during digestion, especially of animal food, that salt being the solvent of gastric juice, according to Blondlot. The urine of carnivora is acid, that of herbivora alkaline, save during fasting, when they may be regarded as feeding on their own tissues. The amount of acidity of the urine of 24 hours equals about that of 30 grs. of oxalic acid. The specific gravity is on average 1.020, but ranging much above and below this even in health, mainly according to ingestion of food; thus, that passed shortly after a meal (urina cibi) has a high density; that passed in the morning (urina sanguinis) a medium, and is most suitable for examination; and that passed after drinking (urina potus) is most watery. The average quantity Dr. Prout stated to be 30 to 40 ozs. daily, the former being the average of summer when the skin discharges so much water, and the latter the quantity passed in winter and moist weather. Dr. Thudichum's average, viz., 65 ozs., is much too high. There is eliminated about 650 grs. of solid matter in this quantity of urine; and this can be always roughly estimated by taking the specific gravity, and multiplying its excess above 1000 by 2.33, according to Dr. Christison's formula. If the specific gravity be then 1.020, the number of grains of solid matter in 1000 grs. of urine will be 46.60, half this if the specific gravity be 1.010, and double it if 1.040. Another simple rule is, that the two last figures of the specific gravity, if under 10.30, give the number of grains of solids in an ounce. Man loses daily by the kidneys about of his weight, and a child nearly twice that amount. Urine forms 46 per cent. of the entire egesta, pulmonary exhalation 32, cutaneous excretion 17, and fæces 4. Urine deposits a cloud of mucus in about 2 hours, or more rapidly if cooled, in which the microscope shows epithelial scales. After some time longer it becomes more highly acid from the formation of lactic acid, which, uniting with the bases of the urates, throws down uric acid. In some instances oxalic acid or oxalate of lime is precipitated. At a still later period it undergoes alkaline fermentation, the urea being changed into carbonate of ammonia, the phosphates deposited, and ammonia, with its characteristic smell, being evolved. This change occurs more rapidly in the bladder, owing to the higher temperature. The Composition of Healthy Urine, specific gravity 1.020, is exhibited in Prof. Miller's analysis: Prof. Day gives the following table of the daily average quantities of the constituents of urine; specific gravity 1.020-52 ounces containing 935 grains of solids : Urine contains, per volume, 45 parts of carbonic acid if fasting, 100 parts if digesting, 8 of nitrogen, and 0.6 of oxygen in the 1000. We shall now examine in detail the most important substances contained in urine during health, and the variations under disease, and firstly the nitrogenized bodies. Urea, which was discovered by Cruikshank, is a weak base uniting with acids, but not showing the other tests of alkaline reaction. It is inodorous, has a cooling, saline taste, and is soluble in its own weight of water. Its composition is shown by the formula C2 H4 N2 O2, and it is metameric with cyanate of ammonia, as discovered by Wohler (H4 N O, C2 N O=C2 H4 N2 O2). It can be prepared artificially. Urine, if evaporated in a watch-glass to, yields crystals of nitrate of urea on adding nitric acid, which can be then removed by carbo th Nitrate of Urea. nate of baryta, leaving the urea pure. It fuses at 248°, at a higher heat gives off carbonate of ammonia, and leaves cyanic acid. The crystals of the nitrate are of the forms seen in the annexed figure.The diurnal quantity is stated most variously by several chemists; thus, Becquerel 295 grains, ton obtained 576 grains from "well-fed, flesh-eating, wine-drinking men, "and but 394 "from well-fed, waterdrinking vegetarians." The last accurate observer gives the following bed-side rule for ascertaining its amount: "Half the excess of specific gravity of urine (not containing either sugar or albumen) above 1000, is the number of grains of urea per fluid ounce." Professor Davy of the Royal Dublin Society has discovered the following beautiful method of quantitative analysis :Place a measured quantity of the fluid containing urea in a glass tube partly filled with mercury, add an excess of solution of hypochlorite of soda, and then invert the tube. The urea is decomposed into water, carbonic acid (which the fluid absorbs), and nitrogen, whose amount in the top of the tube indicates the quantity of urea. The source of urea is either the waste of the nitrogenized tissues, especially muscular, or by the direct destruction of nitrogenized food. Liebig and Bischoff maintain the first view, as it is still excreted after 3 |