The question of distinguishing albumin and mucin precipitations, which Reissner discussed very fully twenty-nine years ago, has been recently again brought before us. The question itself is of no great practical importance on account of the minimal quantity of dissolved mucin contained in clear urine. The fact must be kept in mind, that even highly diluted urine betrays the presence of mucin through the plentiful addition of acetic acid, thus it is necessary in such a case to control the acetic acid heat test with nitric acid procedure. Johnson declares that picric acid only then precipitates mucin when another strong acid is present. Albumin very often accompanies dissolved mucin. Senator and Citron have latterly called one's attention to the fact that the products of decomposition of the cellular substance (nuclein) especially in alkaline and cystitic urines are precipitated by acetic acid, and like mucin remain insoluble in a surplus of acid. F. Müller has already shown the presence of a proteid substance precipitable by acetic acid. In spite of v. Noorden's statement that he has often found mucin in the urine of healthy persons, Senator and Citron conclude that only insignificant traces of mucin are to be found in non-decomposed urine.

Quantitative estimation of albumin.-The best procedure of making an exact quantitative analysis is to coagulate the albumin by means of heat; collect, dry, and weigh it. For the various details we refer to the text-books and manuals of the following authors-Neubauer and Vogel, Hoppe-Seyler, Hofmann and Ultzmann, Löbisch, Zülzer, Huppert, Salkowski, Leube, and Thomas. The practitioner can in a great many cases forego an exact chemical analysis and can replace it by approximate estimation, by simply comparing the degree of coagulation in the test tube with other tests of which the quantitative result is known. Esbach's albuminimetre is of good service, as first proved by P. Guttmann and H. Schulz. It consists of a graduated tube, in which the albumin is precipitated by a solution of picric and citric acid. The results, however, are less reliable the more albumin the urine contains, the more the specific gravity is increased and the lower thet emperature is (Czapek). Zülzer's "Uroscope" is a small tube in form of a U and is based on the similar principle; the albumin is precipitated by solution of concentrated chromic acid. Beginners usually overrate the quantity of precipitated coagulum ; it may serve as necessary information that even a decided cloudiness, which as deposit totally fills the concavity of the test tube, is not above 0.1 per cent., that 1 per cent. albumin renders the urine completely opaque and produces a deposit filling up half of the tube.

If containing three and more per cent. the urine generally becomes coagulated in toto and the masses of albumin brown.*

* Weighing is, as already mentioned, the only way of obtaining an exact quantitative estimate of albumin, for one must always remember that all

Certain French authors follow Bouchard's theory, distinguishing (nephritic) albumin and (dyscrasic) albumin; the former is characterised by a flocky deposit, the latter by an intransmutable regular coagulation.

With regard to practical clinical diagnosis one can for the present do without this distinction. We will only remark that the peptone, which was found by Gerhardt in febrile diseases as latent albumin, i.e., as a precursory sign of albumin, and as elements of pus in pyuria, may be found in urine during the resorption of purulent effusion of pulmonary exudates, etc. (Hofmeister, Maixner, v. Jaksch); the peptone, which does not become coagulable through heat, is thus hemialbumose, an intermediary between peptone and albumin; it was first remarked by Johnson in cases of osteomalacia and has since then been pretty frequently found by Senator, etc., under the most varied circumstances; sometimes it appears as the forerunner of albuminuria (Lassar) or together with it ("mixed albuminuria," Senator). Posner agrees with v. Noorden in supposing that a relationship exists between hemialbumose and the presence of sperma in the urine. For directions to discover the presence of peptone and propeptone in urine see the various treatises on urine tests; no particular value can, however, be attached to it.

Clinical signification of albuminuria.-Those days are long over when the existence of albuminuria, even without engorgement, passed for a characteristic of a renal malady. On the contrary, our firm conviction that at least a tenth part of all healthy persons excrete at times albumin with their urine has brought us to consider the question, whether albuminuria is to be considered in every case as a symptom of illness, or whether it is reconcilable to what is commonly known under the name of "health”.

Physiological albuminuria.-Senator has shown himself to be a firm and staunch upholder of the theory of physiological albuminuria.* Uniting Ludwig's and Heidenhain's theories on the filtration of urine, he considers it as a mixture of the transudation of the glomerular vessels, poor in albumin, and of the nonalbuminous excretion of the urinary canaliculi. According to him the incessant variation of the pressure and rapidity of circulation in the vascular glomeruli, the variability of the excretion of the tubuli uriniferi, suffices to explain the presence or the absence

methods based on judging the amount from the depth of the deposit at the bottom of a tube in relation to the quantity of urine have two fallacies: (1) an individual sample is of a higher or lower specific gravity than another; (2) urates or phosphates, together with mucus casts, granular debris, etc., collect together at the bottom of the tube and thus swell the bulk of deposited albumin.-W. H. G.

Senator declares the quantity of this physiological albumin to be capable of reaching the quantity of 0.4 to 0.5 per litre.--W. H. G.

of physiological albuminuria, according to time and period when the test is made. This theory of Senator has found great support, through the certain proof of traces of albumin in the urine of a normal person (Posner and Leube), as well as through the results of Adam's experiments, who discovered albumin in healthy dogs between Bowman's capsule and the glomerulus, and finally by the latest experimental tests on dogs' kidneys made by Munk and Senator.

Nevertheless, certain authors protest most energetically against the existence of physiological albuminuria, i.e., the fact that albumin is normally excreted by the glomeruli. Greenfield, Coats, Middleton, Rosenstein, Grainger Stewart and J. v. Noorden, conclude a number of systematic observations, with the opinion that in the most cases, in which one can prove albumin in urine of a patient, the careful further observation and examination of the urine gives decided proofs that certain, if only small, pathological processes take place in the uropoietic apparatus; Johnson is also of the same opinion as Bartel, that the presence of albumin in urine is in every case a pathological symptom. Even Leube has of late become much less liberal in accepting a physiological excretion of albumin with the urine. Whether, however, a physiological albuminuria in the above-mentioned sense exists or not, it must be considered as fortunate for the profession that complicated tests are necessary in order to prove albumin in normal urines, be it derived from the glomerular tuft, or from the intermixed formed elements. Were this not the case the diagnosis of albuminuria would soon lose every claim to being important, a fact which would under all circumstances produce most serious consequences. It is natural that the more sensitive the albumin tests are, the more cases there will be in which the physiological albuminuria (as simply quantitative exacerbation) can be proved. We, physicians, must therefore not endeavour to continually discover more sensitive re-agents, because, as we have seen, the reliability will then suffer. On the contrary, practitioners should adopt as much as possible the old and reliable procedures of testing for albumin, should not trouble themselves about small unimportant hazes, but should only reckon with decided deposits, which even at first sight show their importance. Each year of practical clinical experience impresses us more with the importance of this rule.

But even for the case that a physiological albuminuria in the word's strict meaning does not exist, that is to say, that every one cannot be considered to have albuminuric albumin, still there are at the present time such a number of positive experiences due to the fact of testing and observation on healthy individuals, suffering from more or less prolonged albuminuria, that we are in no way justified to consider the presence of albumin as a positive sign of renal disease. It is most important to remember that the

presence of albumin in the urine is merely one particular symptom, and even in tolerable intensity proves no more kidney disease than, for example, a systolic murmur at the mitral valve proves organic heart complaint. The diagnosis depends on the quality and the clinical type offered by the various symptoms.

Classification. Unprejudiced observation proves that it is impossible to strictly distinguish the so-called physiological albuminuria, and such which is produced by other non-renal diseases, from the excretion of albumin caused by coarse anatomical lesions. This difficulty is produced by the existence of various degrees and mixed forms of albuminuria. Nevertheless, we consider it necessary, in order to obtain a general view, to distinguish various forms, the classification of which should be as little schematical as possible. We distinguish, quite apart from the experimental view, five groups, of which we only describe two in this division:

1. Albuminuria in healthy individuals, with and without special cause.

2. Albuminuria in different morbid disturbances where the kidneys are healthy, or at any rate free from evident anatomical lesions.

3. Albuminuria in febrile complaints.

4. Albuminuria with general and local hyperæmia; albu

minuria with stasis.

5. Albuminuria through actual disease of the kidneys, especially through the different forms of nephritis.

In opposition to the albuminuria known as transitory or accidental, one has placed the last form, called persistent albuminuria, as the former is often (1-4) of much longer duration than, for example, the albuminuria in acute nephritis. The distinction between nephrogenous and hæmatogenous albuminuria (Stokvis and Bamberger) is more successful, but the latter term is sometimes promiscuously used for the four first forms and sometimes only for excretion of albumin resulting from modifications in the sanguinary crasis.

1. Albuminuria in healthy individuals with or without special

cause.

66

As Becquerel, Simon and Schmidt have observed a number of perfectly healthy individuals exist who pass albumin in their urine at times, especially after heavy meals and violent exertion of the vascular system. I, myself, know two healthy young men who have the same phenomena.' So spoke Frerichs, nearly

* Herringham describes in the British Medical Journal, 1891, in an article on Cystical or Intermittent Albuminuria," a case of a boy thirteen years old, suffering from intermittent albuminuria. The only cause to which the albuminuria could be attributed was that the boy had remained too long in an upright position. Herringham explains this fact as blood pressure on the renal veins, which, together with weak circulation of the blood, causes venous engorgement in the kidnevs. Connection of albuminuria with the effect of cold or

forty years ago, in his well-known monography on Bright's disease. The abundant experience of the last ten years proves this statement to be true. Vogel observed albumin in healthy persons for years (night-urine free). Ultzmann found albumin in a number of healthy, strong men, partly in consequence of bodily exertion and great excitement, partly so far periodical, that at times albumin was to be found at one time and an hour after it had disappeared; sometimes it remained for days and even weeks. Leube gives us the first precise idea of the relative frequency of the so-called physiological albuminuria through testing the urine of 119 healthy soldiers; five of these soldiers passed albumin directly on rising, and besides these, fourteen after a heavy march (or an average 0.1 per cent.). Munn discovered in a similar manner out of 200 healthy aspirants for life insurance twenty-four with albumin.* We ourselves have often found decided albumin in healthy, blooming young persons, with and without bodily exertion and without reference to meals having just been partaken of; further, in a home for children, out of sixty-one, seven with periodical albuminuria. Periodical albuminuria appeared at intervals of days and weeks, although during this time no change in the manner of living took place, and urine itself presented no variation in quantity and density. We watched the following interesting case for a considerable length of time: a young, apparently perfectly healthy physician, who had undergone violent mental excitement, felt pain in the kidneys; his urine (lessened in quantity) with increased specific gravity, contained 0.6 per cent. of albumin without remarkable morphological deposits. At intervals the urine was entirely free of albumin, and after about a year it returned to its normal condition. The connection of

muscular exertion was not to be found, nor had diet any effect. The greatest secretion of albumin took place in the morning before meat was eaten. Careful testing of the urine for acidity, urea and uric acid did not reveal any connection with the albuminuria.-W. H. G.

* How misleading physiological albuminuria can prove itself the following case demonstrates. A patient came under my treatment suffering from chronic diffused nephritis, the origin of which could be traced back to a severe cold caught some two years previously. In spite of all treatment patient succumbed to the disease a few months after leaving our watering-place. Shortly afterwards his widow communicated to me the fact that the assurance company her husband was insured in refused to pay the premium, the family physician incautiously reporting to have casually detected a trace of albumin six years before, although the company's physician had three years after this proclaimed the urine free of all abnormal constituents, and her husband, on the strength of this satisfactory examination, had been accepted. This, and various other facts, convinced me that the incriminated trace of albumin was merely of a physiological character, and I consequently advised the widow to take proceedings against the assurance company. This she did and the result was satisfactory, the court giving a verdict in her favour, as the company's own physician had not detected albumin and as the possibility of physiological albuminuria existed, and was thus in this case the most probable.-W. H. G.