Neumeister found pepsin in the urine of the dog, but not in that of the rabbit. Neumeister and Stadelmann 2 both showed that the ferment in the urine is true pepsin; it forms peptone and all the intermediate proteoses from fibrin just as pepsin does. Trypsin. Except Sahli, all observers agree that trypsin is absent from the urine. Sahli's results were probably due to the nonprevention of putrefaction in his experiments. Pieces of fibrin soaked in urine, according to Leo's method, are not digested in 1 per cent. sodium carbonate solution, thymol being added to prevent putrefaction. As trypsin is not found in the blood or tissues, Leo concludes that it is entirely destroyed in the alimentary canal; while the pepsin is not wholly destroyed there, but is partly absorbed, and passes into the blood, tissues, and urine. By making extracts of the different parts of the intestine, Leo draws the conclusion that pepsin disappears in the second third and trypsin in the lower third of the small intestine. Diastatic ferment.-Holovotschiner3 states he has obtained small quantities of ptyalin or a similar diastatic ferment from urine. Rennet. - Holovotschiner and Helwes' both obtained from urine traces of a ferment which curdles milk. Mucin. This is the chief constituent of the mucus derived from the urinary passages. It occurs in normal urine in small quantities; in catarrhal diseases of the urinary passages it is increased. It is slightly soluble in neutral and alkaline urines, and may be precipitated therefrom by acetic acid (insoluble in excess) or by alcohol; it is not precipitated by boiling, and so may be distinguished from albumin. It is probably the source of the animal gum found by Landwehr in the urine. Cynurenic and urocanic acids. These are two peculiar acids, the characters of which are described on p. 91, and which hitherto have been found only in the urine of dogs. The former may be precipitated in crystals from urine by nitric acid. They are found in the urine of starving dogs, and so must be products of metabolism, and not the result of putrefaction in the intestines.3 Kryptophanic acid (C,H,NO,) was described by Thudichum as a normal con-stituent of urine, but has not been found by anyone else. Nephrozymase is a substance precipitated by alcohol from urine by Béchamp. According to him, it is proteid in nature. Normal urine, however, is absolutely free from proteids. Urethan (ethyl carbamate) is found in small quantities in the alcoholic extract of normal urine. It is, however, an artificial product of the action of alcohol on urea (Jaffe and Cohn)." 1 Zeit. Biol. xxiv. 272. 3 Chem. Centralbl. 1886, p. 327. 5 Baumann, Zeit. physiol. Chem. x. 123. 2 Ibid. xxv. 208. 4 Pflüger's Archiv, xliii. 384. 6 Ibid. xiv. 395. CHAPTER XLIII THE INORGANIC CONSTITUENTS OF URINE THE inorganic constituents of the urine are chiefly chlorides, carbonates, sulphates, and phosphates; the metals with which these are in combination are sodium, potassium, ammonium, calcium, and magnesium. Small quantities of fluorine, silicic acid, and iron also occur; and the free gases present are carbonic acid and nitrogen, with traces of oxygen. The total amount of salts varies from 9 to 25 grammes daily. The inorganic salts of the urine are derived from two sources: first, from the food; the salts pass into the blood, and then are excreted by the kidneys; secondly, as a result of metabolic processes; this is especially the case with the phosphates, and more particularly still with the sulphates. The salts of the blood and those of the urine are much the same, with the important exception that, whereas the blood contains only traces of sulphates, the urine contains abundance of these salts; the sulphates are derived from the changes that occur in the proteids of the body; the nitrogen of the proteids is excreted as urea and uric acid; the sulphur is oxidised to form sulphuric acid, which passes into the urine chiefly combined with metallic bases, but to a small extent also in ethereal combinations with organic radicles to form the ethereal sulphates we have already considered (p. 740). The excretion of sulphates, moreover, runs parallel to that of urea. The tests for the chief salts are given on p. 717. Their estimation is described in Chapter XLV. THE CHLORIDES The principal chloride in the urine is that of sodium. Small quantities of potassium chloride and traces of calcium and magnesium chloride are also present. Sodium chloride is, in fact, the most abundant salt in the urine, as it is in the blood and in most other fluids of the body. Vogel gives the daily amount of chlorine excreted as 6 to 8 grammes, which would correspond to 10 to 13 grammies of sodium chloride. The ingestion of sodium chloride in the food is followed by its appearance in the urine, some on the same day, some on the next day (Dehn 1); some, however, is decomposed to form the hydrochloric acid of the gastric juice. The sodium chloride, however, does not merely pass through the body without making its effect felt; it stimulates metabolism and secretion, as has already been pointed out (p. 61). The urine is richest in sodium chloride after a meal; poorest at night time." Drinking large quantities of water or beer increases it; a rich secretion of gastric juice causes a temporary decrease in the chlorides of the urine. Certain chlorine compounds other than chlorides causes an increase of the urinary chlorides: chloroform narcosis, and the administration of ethyl trichloracetate act in this way; whereas certain other chlorine compounds (chloral,3 carbon tetrachloride, methyl chloride, &c.) do not have this effect (Kast 6). 4 The quantity of chlorides excreted varies greatly in disease:-It is diminished in most febrile diseases; the cause of this is unknown, but is, perhaps, partially due to diminished intake of the salt, or in some cases to diarrhoea, by means of which a certain quantity of salt passes out per rectum (see p. 699). The decrease is especially marked in pneumonia, pleurisy, and typhoid fever, and runs parallel to the height of the fever. In pneumonia the chlorides may entirely disappear from the urine, their reappearance being one of the signs of improvement. It is diminished in cholera, chorea, and pemphigus. It is increased in diabetes, polyuria, and some forms of Bright's disease, where a large amount of urine is excreted. The relation of sodium and potassium salts in some of these conditions has been investigated by E. Salkowski. In health the ratio is variable, depending to some extent on diet. In febrile conditions in which the total chlorides are diminished the excretion of the potassium salt rises above the average. Zuelzer' states that the same occurs in conditions of excitement. THE SULPHATES The sulphates in the urine are of two kinds, ordinary sulphates of potassium and sodium (pre-formed sulphuric acid), and ethereal sulphates (combined sulphuric acid). They are derived in small measure from the food (administration of sodium or magnesium sulphate increasing the quantity of sulphates in the urine), but chiefly from the metabolism of proteids in the tissues. The ethereal sulphates are the result of putrefaction of proteids in the intestines or elsewhere, as in a putrid abscess. The sulphates of the urine may vary in amount from 1.5 to 3 grammes daily (Furbringer, 10 Neubauer 11). The administration of free sulphuric acid to dogs increases the urinary sulphates 12; in rabbits this is not the case. 13 1 Pflüger's Archiv, xiii. 353. A. Hegar, Ueber d. Ausscheidung d. Chlor durch den Harn, Giessen, 1852. 3 Chem. Centralbl. 1887, p. 1561. 4 Zeller, Zeit. physiol. Chem. viii. 70; Kast, Ibid. ii. 277. Chloral passes into the urine as urochloralic acid (v. Mering). 7 Pflüger's Archiv, iii. 351. 9 Sick, Diss. Tübingen, 1859. 11 Neubauer and Vogel's Text-book. 6 Loc. cit. 8 Centralbl. med. Wiss. 1877, Nos. 42 and 43. 10 Arch. path. Anat. lxxiii. 39. 12 Frey and Gähtgens, Centr. med. Wiss. 1872, No. 53; Kurtz, Diss. Dorpat, 1874. 13 Salkowski, Arch. path. Anat. lviii. 1. The variations of the amount of urinary sulphates in disease can be almost guessed after the statement has been made that their amount runs parallel to that of the urea excreted. In conditions where metabolism is increased (fever, diabetes) the sulphates are increased; in conditions where metabolism is diminished (convalescence from fever, most chronic affections) the sulphates are diminished. Bence Jones states that an increase occurs in various forms of delirium; also in acute inflammatory diseases of the brain and spinal cord. THE CARBONATES Carbonate and bicarbonate of sodium, calcium, magnesium, and ammonium are generally present in fresh, alkaline urine. They arise in the organism from carbonates of the food, or from lactic, malic, tartaric, succinic, and other vegetable acids in the food. They are thus most abundant in the urine of herbivora and vegetarians, whose urine, we have already seen, is thus rendered alkaline. Urine containing carbonates is either cloudy when passed or, like saliva (see p. 622), soon becomes so on standing; the deposit, if allowed to settle, will, on examination, be found to consist of calcium carbonate and also phosphates. THE PHOSPHATES Phosphoric acid in normal urine occurs in the form of two classes of phosphates : (1) Alkaline phosphates. Phosphates of sodium are the most abundant; those of potassium scanty. (2) Earthy phosphates. Phosphates of calcium are the most abundant; those of magnesium scanty. The composition of the phosphates in urine is liable to variation. In acid urine, the acid salts are generally present, and give the urine an acid reaction. These are chiefly sodium dihydrogen phosphate (NaH2PO4) and calcium dihydrogen phosphate [Ca(H,PO4)2]. In neutral urine, in addition to these, phosphates with formulæ Na2HPO, (disodium hydrogen phosphate), CaHPO, (calcium hydrogen phosphate), and MgHPO, (magnesium hydrogen phosphate) are also found. In alkaline urine there may be in addition to, or instead of some of, the above the normal phosphates of sodium, calcium magnesium [Na3PO4, Ca3(PO4)2, Mg3(PO4)2]. In addition to these, phosphoric acid may be united to the bases ammonia, urea, and creatinine. The earthy phosphates are precipitated by rendering the urine alkaline by ammonia, potash or soda, or in the ammoniacal fermentation that occurs in decomposing urine. The alkaline phosphates remain in solution after the earthy phosphates have been precipitated in this The phosphates found most frequently in the white creamy way. precipitate that occurs in decomposing urine are (1) the triple phosphate (ammonio-magnesium phosphate, NH,MgPO ̧+6 H ̧O), which crystallises in triangular prisms, or so-called 'coffin-lid crystals' (fig. 99), Magnesium or Triple Phosphate. and occasionally in feathery stellate crystals; (2) calcic phosphate, often called 'stellar phosphate,’ which crystallises in star-like clusters of prisms. In acid urine a crystalline calcium phosphate occasionally separates out; it may also be obtained by adding calcium chloride to urine, or, after the internal administration of lime-water, or potassium carbonate. It has the composition CaHPO1+2H,0 (Hill Hassal,' Stein 2). Normal urine gives no precipitate when it is FIG. 99. Ammonio- boiled. Neutral, alkaline, and, occasionally, faintly acid urine give a precipitate of calcium phosphate when boiled; this precipitate is amorphous, and is liable to be mistaken for albumin; it may be distinguished readily from albumin, as it is soluble in a few drops of acetic acid, whereas coagulated proteid does not dissolve. Salkowski 3 showed that the precipitated phosphates often redissolve when the urine cools. There have been various explanations advanced to explain the precipitation of phosphates by heat. They all, however, may be summed up by saying that the phenomenon is the result of unstable equilibrium among certain phosphates, the balance of solubility being easily disturbed by changes of temperature and reaction, and possibly modified by the kind and amount of other salts in solution (W. G. Smith,1 Stokvis"). The precipitation was believed by some to be due to evolution of carbonic acid. Salkowski attributes it to the decomposition of a compound of calcium an sodium phosphate. Reynolds suggests that the change produced by heat may be represented as follows: = 2CH(FO)2+CaH,(PO,), Ca,(PO,). (insoluble) + 2CaH,(PO,), (soluble). A. Ott speaks as follows on the subject. Erlenmeyer has shown that acid calcium phosphate is soluble in 700 parts of water. But the urine is able to hold more than this in solution, in virtue of the presence of other salts. Similarly the normal phosphate is more soluble in urine than in water, such salts as potassium phosphate and sodium chloride aiding its solution. By heating an aqueous solution of the two phosphates the acid phosphate is changed into the normal phos 1 Proc. Roy. Soc. x. 281. 3 Zeit. physiol. Chem. vii. 119. p. 1839. 2 Liebig's Annalen, clxxxvii. 90. Dublin Journ. Med. Sci. July 1883. Zeit. physiol. Chem. x. 167. |