158 : 1000 : : 3.85 : x (:= 24.37) casein per 1000.
. .
The proportion of " extractive matter " in milk varies, but I am not aware of any ready method of determining its'quantity, apart from that of the sugar-ind-e-a-sein. If we attempt to digest casein in water, it swells up and partly dissolves, becomes gelatinous, and does not allow the fluid to pass through the pores of the filter. If a cold saturated solution of sugar of milk in proof spirit, (sp. gr. 920,) be allowed to digest for a few days in a closed flask upon the spirituous extract (d), the liquid assumes a yellow colour from dissolved extract, and the sugar is left in white crystalline pains, but this can hardly be used as a process for analysis.
4. Analysis of bile.
Our methods for analysing this complicated and important secretion are very inadequate. Still, such as they are, I have endeavoured to illustrate them by the following example: The bile analysed was obtained from a man ret. 75, who died of gangrena senilis. The gall-bladder was removed entire, and the bile examined 48 hours after death.
It was a brownish, turbid, scarcely ropy fluid, of sp. gr. 1024, and amounted to about 240 grs.
(a) 65.16 grs. evaporated to dryness left 4.83 grs. This residue on incineration left 0.75 grs. of saline matter.
65,16 : 1000 : : 0.75 : x (= 11.51)saltsper 1000.
4.83 - 0.75 = 4.08 and 65.16 : 1000 : : 4.08 : x (= 62.61) organic matter per 1000.
Therefore 1000 - (11.51 62.61) = 925.88 water per 1000.
(b) 171.2 grs. mingled with thrice its bulk of alcohol, and filtered, left a yellowish ropy residue of mucus, which, when well washed with alcohol and dried, amounted to 5.1 grs.
171.2 : 1000 : : 5.1 : x (= 29.78) mucus per 1000.* (c) The filtered liquid was evaporated nearly to dryness and mingled with ether. A bright yellow solution was obtained ; it was decanted, and the residue repeatedly digested with ether. The mixed ethereal solutions, on evaporation, left 2.8 grs., of which 0.6 grs. was soluble in water (being biliary matter).
2.8 - 0.6 = 2.2 ethereal extract.
(d) The ethereal' extract was treated with a weak solution of ammonia; a brown liquid was obtained, and a white crystalline residue of cholesterin was left, amounting to 0.31 grs.
171.2 : 1000 : : 0.31 : x (= 1.81) choles terin per 1000 2.2 - 0.31 1.89. • 171.2 : 1000 : : 1.89 : x.(= 11.04) uncom binedfatty and resinous acids per 1000.
(e) The residue insoluble in ether was treated repeatedly with hot alcohol. It left undis solved a remainder, vvhich when dry amounted to 2.92 grs.
171.2 : 1000 : : 2.92 : x (= 17.05) watery extract.
(f) An attempt was made to separate the colouring matter from the alcoholic extract by baryta water, and to obtain it free from baryta by solution in carbonate of ammonia, but it did not succeed ; indeed I have never been able by this or any other process to separate the colouring matter from the other ingredients of the bile with sufficient accuracy to warmnt its adoption for analytical purposes.
(g) The quantity of alcoholic extract was in this case from tile experiment with the baryta necessarily inferred from the deficiency.
Since 1000 grs. contain 74.12 of solid mat ters, 171.2 grs. will contain 12.60 ; we must, therefore, deduct the ethereal and watery ex tract, and mucus : (2.2 + 2.92 -1- 5.1) = 10.22 grs.
12.69 - 10.22 = 2.47. Hillary and co louring matter : 171.2 : 1000 : : 2.47 : (= 14.37) biliary matter per 1000.
M. Pettenkofer has recently proposed the change of colour produced by the action of sulphuric acid and sugar upon bile as a test of its presence. Having freed the liquid sus pected to contain it from albumen by evapo rating to dryness and exhausting the residue by boiling water, the solution is concentrated by evaporation, and when cold mingled with about one-third of its bulk of oil of vitriol, so as to raise the temperature of the mixture ftom 150° to 160° of Fahrenheit, but not higher. A few grains of sugar are now added to the liquid, and the whole suffered to stand for a few minutes. If bile be present a beautiful crimson colour is developed, increasing in in tensity for some minutes. The tint is un equivocal provided the solution contain not less than of its weight of dry bile, or -st, of the recent secretion. This reaction is independent of the mucus and colouring matter.