THALLOGENS. Thallogens or Thallogenous plants are structurally the simplest of the acotyledonous, or flowerless plants, consisting simply of a collection of cellular tissue, called a thallus. They are entirely destitute of woody fibre. The Algæ, Characeæ, Fungi, and Lichens are thallogenous plants.
THEBA′INE. C19H21NO3. Syn. Thebaia, Paramorphia. A crystalline substance obtained by Thibourméry from an infusion of opium that has had its morphia extracted by acting on it by an excess of lime.
THE′INE. C8H10N4O2. Syn. Theina. An alkaloid extracted from tea. It is identical with caffeine, and may be obtained from tea in the same manner as that substance is from coffee. The best ‘gunpowder tea’ contains fully 6% of theine, about one half of which is lost in the present careless mode of making infusion of tea for the table.
Mr Lewis Thompson, M.R.C.S., in a contribution to the ‘Medical Times and Gazette’ for 1871, directs attention to the value of theine as a therapeutic agent, as well as gives an easy method for its preparation. He writes as follows:—“I wish to direct the attention of the medical profession to a valuable agent which has hitherto escaped notice, although its powers are most unquestionable, and its cost price very trivial. The article to which I allude is theine, a substance existing in tea and coffee, and, as I believe, in many other vegetable products.
“As a medicine, theine is powerfully tonic and stimulant, and appears to possess the tonic virtues of the disulphate of quinia united to the stimulating power of wine, but with this difference, that the stimulus from theine is not followed by depression, as in the case of wine and alcohol.
“Theine seems to act chiefly on the great
sympathetic or ganglionic system of nerves, and but slightly on the brain. I have used it in doses of from 1 to 5 grams, with very marked advantage, in the low stage of typhoid fevers, confluent smallpox, and that form of mortification of the toes which is so singularly fatal to old people. But, in addition to this, different medical friends of mine have found it useful in hemicrania, neuralgia, and what has been called relapsing fever; and in the case of an overdose of opium, it appeared to relieve the narcotic symptoms speedily.
“With regard to the cost of this medicine, I have discovered that in the ordinary process of roasting coffee, the whole of the theine is driven off before the torrefaction of the coffee is completed; and thus theine may be cheaply collected by making the axis of the coffee roaster tubular. If, instead of a solid axis, we employ at one end of the roasters a tube passing away to the distance of about three feet, the theine is condensed in this tube by the refrigerating power of the atmosphere, and may afterwards be easily dissolved out by a little water, and purified in the manner about to be indicated.
“As the result of much experience, I have obtained on an average, 75 grains of theine from the roasting of 1 lb. of raw coffee; and when we reflect that in Great Britain alone, there are more than 13,000 tons of coffee roasted annually, we see that about 140 tons of theine are wasted and lost every year by sheer ignorance. It may, perhaps, be thought that the saving of the theine will damage the flavour of the coffee, but from experience I know that it has no such effect; and, in point of fact, it is an advantage to the flavour of the coffee to make both the axes of the roaster tubular, and to cause a gentle current of air to pass through the apparatus during the roasting of the coffee, so as to expel the empyreumatic products that are formed. I will now relate the fact upon which the purification of theine depends, and when this is once clearly understood, the manufacture of theine from either tea or coffee becomes an extremely simple matter. Theine is absolutely insoluble in a concentrated solution of the carbonate of potash, and thus we may precipitate it from its admixture with sugar, mucilage, and vegetable extract. If, then, by means of the subacetate of lead, we have removed from a vegetable infusion the tannin, malic acid, &c., we have only to evaporate the filtered solution to a small bulk, and add to it its own weight of dry carbonate of potash, and the whole of the theine becomes at once insoluble; so that having collected this insoluble product, and boiled it in rectified spirits of wine, we have a solution of pure theine, which, after distilling off the spirit, furnishes crystals fit for immediate use. In conclusion, I will merely mention a distinctive test for theine, sufficiently delicate to detect the one thousandth of a grain of that substance. Dissolve the theine
in a small quantity of water, and pass through this a stream of euchlorine, then allow the fluid to evaporate at a steam heat; a blood-coloured substance will remain, which, on the application of a few drops of cold water, forms a beautiful scarlet solution like red ink. It is, I apprehend, almost unnecessary for me to say that euchlorine gas is formed by the action of hydrochloric acid upon the chlorate of potash.