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seems the most perfect. It depends upon weighing the nitrogen in combination, and then the other substances left after its decomposition and escape. It may be denominated the plan of double weighing or the method of differencesand where proper precautions are taken, is simple, cleanly, and quite accurate. The operation is performed in a bottle, the neck of which is large enough to admit a drachm or larger vial attached to the bottom of a cork by string or wire. The small vial is intended to be placed uncorked in the larger one, and to contain a measured quantity of urine. The larger bottle holds the tests, which are either Labarraque's solution and solution of salt or hypobromate of soda solution. When we desire to make a determination the larger bottle is half filled with the test fluid (for rapidity the hypobromate of soda is preferred), and the small one with a measured quantity of urine. The small vial suspended from the cork is now carefully thrust into the neck of the other bottle, so as not to spill its contents, and the cork is pressed tightly into place. The whole is then carefully weighed, the amount noted, and the bottle turned upside down and shaken, so as to mingle the contents. After, or even before, complete decomposition, if the pressure be great, and to insure accuracy, the cork must be slightly removed, and when all the gas has escaped, provided decomposition is over, it is to be reweighed, and the difference between the two will represent the weight of the escaped nitrogen.
The weight of this gas being known, the quantity of urea can at once be calculated from a table. Another method, called the specific gravity one, depends upon the property of pure sulphate of lime (that has been washed with absolute alcohol) to form a solid with water or urine. This solid is then to be powdered, and its urea dissolved out by absolute alcohol, when the specific gravity apparatus will give us the amount of urea contaminated with a slight quantity of extractive, or the alcohol may be allowed to evaporate spontaneously, and the urea can then be directly weighed. For those who have no scales, I have devised other simple forms of apparatus, such as the U tube, to contain mercury salt and water, with Labarraque to decompose the urine, which is brought in contact with it by a hypodermic syringe inserted through a cork at the bottom or top, or a float bottle to contain the urine may be used for the same purpose. The nitrogen that collects in the upper part of the apparatus
(Fig. 2), can be directly measured by the graduation upon it. In another form a mercurial column in a manometer tube is
directly acted upon by the pressure of the nitrogen, as it is disengaged by the chlorinated soda in the bottle, and the quantity can be told at a glance (Fig. 3). The urine in this case may be introduced through the manometer tube by means of a piston, by a float bottle inserted before the cork that contains the manometer tube is placed in position, by spun glass used as an absorbent for the urine that can be stuck round the tube and afterwards be shaken off, or by attaching a small bottle to the manometer tube, as had previously been done when the first or double weighing process was described. With the latter method, the bottle and manometer has to be turned on its side or upside down, so as to mingle the urine with the tests, and one end of the manometer tube will then have to be closed by the finger, or an India-rubber stopper, or one of the rubber caps that are met with on the common drop tube. I have tried a number of other modifications that are well worthy of mention, but time forbids their description. Other secretions or excretions can be examined by like simple tests, so as to obtain a very fair idea of the wantsof the whole body.
The quantity of a remedy that is required can only be determined by what is known concerning its average effects, and depends upon the condition of the absorbents or pores of the sys
tem at any given time. Thus, if we have reason to think that the natural pores are stopped up, or reduced in calibre, or obliterated, it is useless to present substances that are too large to enter them, and if such remedies are essential they will either have to be reduced in size, or, if this is impossible, a new route by the rectum, or hypodermic syringe will have to be chosen. The special preparation, that both foods and medicines require, has been left too much in the hands of the cooks and druggists, but it is wonderful to note how mankind has been led to act physiologically without such intention. In the choice of food used in the raw state, if Dr. Roberts is to be credited, but two animal substances are suitable to be thus employed, and these are milk and oysters. The first has been specially prepared by the animal economy, and is looked upon as the ideal food, and the second contains within its liver the two substances, glycogen and a ferment that when mingled are requisite for its digestion. A proof that the oyster possesses this power has lately come under my own observation, which may be worthy of description. A gentleman, who had suffered for three years from a small quantity of sugar in the urine, due to slight brain trouble that caused temporary paralysis, informed me last winter that whenever he ate raw oysters the specific gravity of his urine increased from about 1013 to 1028. Anxious to see if this was not a mere coincidence he was directed to refrain from the use of the bivalve, except on four special occasions at an interval of three days, when, sure enough, the specific gravity and sugar both increased in such proportion as to leave no possible doubt.
I should like very much, if time permitted, to call attention to some experiments that I have made upon porosity, endosmose, etc., by various physical means, especially the spectroscope, and to speak of the modifications that occur to foods or medicines from dilution, digestion outside the body, cooking, Papin’s digester, etc.; but for the present must be content to refer to improvements of flavor. The importance of this subject can hardly be overestimated, since it is the key to gain access to many a disgusted stomach, and on which turns much of our success as practitioners.
The most difficult substances in our experience to improve belong to the class of fats or oils, and many have been the attempts to render them tolerable to palate and stomach. The most successful depend upon overwhelming the sense of taste
by highly pungent or aromatic oils, or by dilution so as to scatter the particles, in hope that the tongue will come in contact with but few of them. Another plan has been to emulsify, so as to mechanically cover over each globule, or mingle with some solid like that from which the oil was originally taken. Cod-liver oil, one of the best restoratives, has thus been prepared, and in the form of jelly, emulsion, soapy material, glyceroid, liquor, in capsules, etc., has long engaged attention. It has lately been used in combination with beer, phosphates, glucose, and dextrine, as put up by Dukehart in our city, where the bitter of the hops and sweet of the maltose render it quite agreeable to many palates and stomachs. A keen sense of taste, however, can often detect it, and where the flavor is entirely to be disguised it is absolutely necessary to adopt some other plan. Cheese affords an excellent vehicle for those who are fond of it, as it not only covers the taste, but by its pungency acts upon the oil so as to put it in the most favorable condition to be emulsified and digested. Where cheese is objectionable bread may be substituted, or it can be disguised by the vinegar, salt, and spices of a salad, substituting this for salad oil. It can also be added to the cod fish balls consisting of fish and potatoes, so commonly eaten in New England. The taste of other unpleasant restoratives may be modified in a similar manner by using something pleasant that they most nearly resemble. One important object accomplished by rendering the flavor pleasant is to keep the substance for a longer time in the mouth, so as to enable it to be disintegrated and mingled with the saliva. Because the saliva has no chemical or fermentive action upon certain classes of remedies, is no reason that it is not useful, for there are two other mechanical effects that are very essential, namely, a rending asunder of particles from the carbonic acid that is generated from the carbonates when the food reaches the stomach, and an expansion of the air from heat that is held in meshes by this viscid fluid. The power of the saliva, both as a solvent, diluent, separator, etc., is not half appreciated, even by physiologists, otherwise there would not be the indifference that is daily seen conceruing its quantity, constitution, reaction, and specific gravity. In the infant, for instance, of but a few weeks, who has no starch to digest, what is the use of the abundant supply of this fluid we sometimes see? Does it not at times even do harm and call for some remedy like belladonna to check its secre