gravimetrical analyses is scientifically and practically not worth one accurate analysis.

The reader is now in possession of the facts which will enable him to attribute its proper value to the gravimetrical method of determining the amount of solids in the urine. The following observations are recorded in tabular order as being the best of their class:

Ob servers.

Prout.

G. Bird

Becquerel

Average quantity

MEN.

of urine in twenty- Average density.
four hours.

Quantity.

WOMEN.

Min. Med. Max. Min. Med. Max. Min. Med. Max. Min.

Routh, eighteen observations. 20

35 50

1.021

mean 1.017

According to the older estimates, the kidneys seemed to excrete from 600 to 700 grains of solids in twenty-four hours (mean 650, Dr. G. Bird). However, all the late authors coincide in making 1020 the average specific gravity of urine, and if of this urine from 1400 to 1600 grammes (19 to 56 fl. oz.) are discharged during twenty-four hours, the gravimetrical method gives a mean amount of solids of from 55 to 66 grammes, or 850 to 1020 grains for twenty-four hours.

100 kilogrammes of individual discharge on an average 41 grammes of solids per hour, 100 centimetres discharge 15 grammes (Vogel).

For the generality of diseases the gravimetry of urine gives very meagre results as yet, but there can be no doubt in the abstract that an accurate knowledge of the whole amount of solids would be of high practical value in every case of illness. The amount of nourishment acquired from ingested food, the intensity of the destruction of matter serving the purposes of life, as found by the comparison of times and quantities, the activity of the secreting organs themselvesall these factors are summed up in the total quantity of solids contained in the urine. It is natural then that in disease

generally, where little solid food is being taken, the amount of solids sinks from the daily 60 to 50 and 40 grammes (600 grains), and even then is made up less of the produce of the destruction of fresh nourishment in the blood and muscles than of disintegrated tissues and their interstitial juices; in other words, is formed mostly at the expense of the body, as is entirely the case in simple inanition. A patient lives on his own fat partly during his illness, as the proverb says, like a badger during the winter. The consequences are clearemaciation.

I have now spoken of disease generally; and the remarks made of course apply to the two great classes of disease, acute and chronic, with equal force. But the fluctuations in the amount of solids occurring in both are of a very different prognostic value; for in chronic disease, with a limited amount of solids, a rise in their amount is, as a general rule, a forerunner of considerable and mostly lasting improvement, and indicates that the chemistry of the body is actively employed in renewing the material of the organs and rectifying their functions. To this rule diabetes mellitus alone forms an exception, where a rise in the amount of solids indicates an exacerbation of the disease; and, in this respect, diabetes forms the transition from chronic to acute disease, in which, on the whole, a rise in the amount of solids in the urine during the acme is an unfavorable symptom, indicating an excessive disintegration of the tissues and juices of the body, which must necessarily lead to exhaustion of the material substrata of life. Under all circumstances, a constant and gradual decrease of the amount of solids is as unfavorable a symptom as the decrease of the total quantity of urine discharged, because it indicates the decay of life, and a probable fatal termination of the case.

The indications of the solids become more varied as soon as they are considered with relation to the amount of other excreta. First, as regards the amount of water by which they are accompanied in the urine, four distinct classes of cases must be borne in mind. If a very small amount of solids is contained in a similar amount of water, we may conclude upon a corresponding amount of anæmia in the individual, always provided that disease of the kidney be not present. In the latter case, a small amount of solids indicates the retention of urea, which may probably end in uræmia.

If a small amount of solids is contained in a larger or large amount of water, it may possibly be the consequence of excess of drink of some kind. Many cases of hysteria,

of anæmia with hysterical symptoms, are accompanied by this description of urine. It is the essential symptom of a decided improvement in many cases of hydræmia and dropsy, and when it occurs in a patient with no particular cause to account for it, it has properly been termed hydruria. Of this disease Professor Vogel observed a very decided, and therefore illustrative case. A man, thirty-five years of age, of a powerful frame, and suffering from rheumatism of the neck, discharged a quantity of urine, amounting to 2983 c.c. (104 fl. oz.) per day in the mean of twenty-four days. But its specific gravity was very low, varying between 1005 and 1012; and the average quantity of solids discharged per day accordingly only amounted to 42 grammes (630 grains). This case was therefore clearly one of hydruria. The patient did not seem to suffer under this excessive discharge of fluid.

When the amount of solids becomes larger, but still remains below the standard of health, and the amount of water is at the same time diminished-in other words, in diseases with a small amount of urine of high specific gravity-the acuteness of the pathological process is clearly indicated. Beginning with the physiological excessive perspiration, there are many pathological conditions, as the sweat of fever, thirst, starvation, diarrhoea, and fever of essential or symptomatic nature, of which this condition of urine is a regular symp

tom.

In the fourth class of cases, both the solids and the water of the urine are present in excess. They form a special and specific class of diseases, to which the generic name of diabetes has been given. The genus has, however, only two species, of which the one is distinguished by the presence in the urine of sugar, and therefore goes by the name of diabetes mellitus; the other subdivision comprises cases where, in a large amount of water, the increased amount of solids is made up of other solids than sugar, termed diabetes insipidus. In both classes of diabetes, the wear of the body is considerable, and either at intervals, or throughout the course of the disorder, surpasses the amount of nutriment taken in. Diabetes mellitus, from its chemical interest, and the facility with which it may be artificially produced in animals, has been favoured with more attention of late than diabetes insipidus, a disease with which perhaps many difficult cases of hysterical anæmia and intractable ailments will have to be classed hereafter. If the total quantity of urine amounts to more than 3000 c.c. (105 fl. oz.) per day, and if the specific gravity shows an excessive amount of solids, ranging from the normal

42

SOLIDS AND WATER: SPECIFIC GRAVITY.

60 grammes (926 grains) up to 130 grammes (2006 grains), or even more, giving on an average about 80 grammes (1234 grains) per day, we may then with perfect safety ascribe the excessive destruction of the constituents of the body to this excesssive secretion, and place to its account a number of symptoms usually following in its train, such as the pale looks and the headache of anæmia, vertigo, the tenderness of certain dorsal vertebræ on pressure, and spasms in the muscles of the neck, such as were observed by Vogel in a marked case of this description.

We have now considered in its bearings the observation of the amount of solids in relation to the water in which they are contained; it only remains to draw attention to the important conclusions to be derived from comparing the amount of solids secreted by the kidneys with the excreta of the skin, lungs, and bowels. In many cases of dropsy, the bowels will spontaneously compensate partly for a diminished discharge of urine; and it is, in fact, by this vicarious discharge that drastic purgatives are of service in disease of the kidneys. The skin will eliminate urea in cholera in such quantities that it may be collected by washing and crystallization, and its amount may even be determined. The lungs will, perhaps, in many cases take on increased action, and discharge, not only water, but also carbonic acid, to compensate for a diminished secretion by the kidneys and skin. diminution in the amount of solids in the urine requires therefore to be checked by the amount of vicarious discharges. And should we be able to determine at the same time the amount of the ingested nutritive matters, we should at once be in a position to balance the income and expenditure of the body, and thereby not only to foresee the probable result, but also to be in possession of the indication for part of our treatment. But in this direction so much remains to be ascertained by fact, that it would be dangerous to the practical tendency of these pages to mix up prospective speculation with the real advantages to be derived from observation of the amount of solids discharged in the urine.

THE best physiological definition of urea is perhaps the following: Urea is the principal product of the metamorphosis in the body of nitrogenized food. It is essentially excretory matter, incapable of any longer serving the purposes of life, because it cannot be more highly oxydized; and when retained becomes a poison to the system,' both directly, and, perhaps, by the products of its decomposition. Its regular occurrence in healthy blood, and in the juice of flesh of animals and man, has established the opinion that it is formed in the tissues (muscles), and carried by the blood to the kidneys to be discharged. Hence, when the action of the kidneys is partially or totally suspended, urea naturally accumulates in the blood, and accompanies the serum effused into the cellular tissue and the cavities of the body.2 In this way its occurrence in the dropsical fluid of Bright's disease, as first discovered by Rayer and Guibourt, and confirmed by subsequent observers, and in the blood of animals after extirpation of the kidneys (Prevost and Dumas), is satisfactorily explained. In cholera the condition of the blood forms the obstacle to the excretion of urine, and in consequence urea is found in the blood, and in the viscid perspiration of the skin. Urea has been discovered in the vitreous and aqueous humours of the eye. It has been found in the

3

' Gallois, 'Essai physiologique sur l'Urée et les Urates.' Thèse offerte à la Soc. d. Pharm. Journ. de Pharm. et de Chim.,' 3me ser., tome xxxii, p. 64. • De l'action toxique de l'Urée.'

2 S. Picard, De la présence de l'Urée dans le sang, et de sa diffusion dans l'organisme.' Thèse. Strasbourg,' 1856, Canstatt's Jahresber., p. 169.

Desire, Gaz. Méd. de Paris,' 1836, Juill.

Marchand, Müller's Archiv,' 1837, p. 440.

Marchand, Erdmann's Journal,' 1837, xi, p. 449.

Millon, Compt. Rend.,' xxvi, p. 121.