COATING OF THE EMBRYO.This membrane (6), which is only an expansion of the embryo, surrounds the endosperm; it is composed of beautiful irregular cubic cells, diminishing according as they come nearer to the embryo. These cells are composed, first, of the insoluble cellular tissue; second, of phosphate of chalk and fatty phosphoric bodies; third, of soluble cerealine. In order to study the composition and the nature of this tissue, it must be completely isolated, and this result is obtained in the following manner.
The wheat should be damped with water containing 10 parts in 100 of alcoholized caustic soda; at the expiration of one hour the envelopes of the pericarp, and of the testa Nos. 2, 3, 4, 5, should be separated by friction in a coarse cloth, having been reduced by the action of the alkali to a pulpy state; each berry should then be opened separately to remove the portion of the envelope held in the fold of the crease, and then all the berries divided in two are put into three parts of water charged with one-hundredth of caustic potash. This liquid dissolves the gluten, divides the starch, and at the expiration of twenty-four hours the parts of the berries are kneaded between the fingers, collected in pure water, and washed until the water issues clear; these membranes with their embryos, which are often detached by this operation, are cast into water acidulated with one-hundredth of hydrochloric acid, and at the end of several hours they should be completely washed. The product obtained consists of beautiful white membranes, insoluble in alkalies and diluted acids, which show under the microscope beautiful cells joined in a tissue following the embryo, with which it has indeed a striking analogy in its properties and composition. This membrane, exhausted by the alcohol and ether, gives, by an elementary analysis, hydrogen, oxygen, carbon, and azote. Unfortunately, under the action of the tests this membrane has been killed, and it no longer possesses the special properties of active tissues. Among these properties three may be especially mentioned:
1st. Its resistance to water charged with a mineral salt, such as sea salt for instance
2d. Its action through its presence.
3d. Its action as a ferment.
The action of saltwater is explained as follows: When the berry is plunged into pure water it will be observed that the water penetrates in the course of a few hours to the very center of the endosperm, but if water charged or saturated with sea salt be used, it will be seen that the liquid immediately passes through the teguments Nos. 2, 3, 4, and 5, and stops abruptly before the embryo membrane No. 6, which will remain quite dry and brittle for several days, the berry remaining all the time in the water. Should the water penetrate further after several days, it can be ascertained that the entrance was gained through the part No 10 free of this tissue, and this notwithstanding the cells are full of fatty bodies. This membrane alone produces this action, for if the coatings Nos. 2, 3, 4, and 5 be removed, the resistance to the liquid remains the same, while if the whole, or a portion of it, be divided, either by friction between two millstones or by simple incisions, the liquid penetrates the berry within a few hours. This property is analogous to that of the radicules of roots, which take up the bodies most suitable for the nourishment of the plant. It proves, besides, that this membrane, like all those endowed with life, does not obey more the ordinary laws of permeability than those of chemical affinity, and this property can be turned to advantage in the preservation of grain in decortication and grinding.
To determine the action of this tissue through its presence, take 100 grammes of wheat, wash it and remove the first coating by decortication; then immerse it for several hours in lukewarm water, and dry afterwards in an ordinary temperature. It should then be reduced in a small coffee mill, the flour and middlings separated by sifting and the bran repassed through a machine that will crush it without breaking it; then dress it again, and repeat the operation six times at least. The bran now obtained is composed of the embryous membrane, a little flour adhering to it, and some traces of the teguments Nos. 2, 3, 4, and 5. This coarse tissue-weighs about 14 grammes, and to determine its action through its presence, place it in 200 grammes of water at a temperature of 86°; afterwards press it. The liquid that escapes contains chiefly the flour and cerealine. Filter this liquid, and put it in a test glass marked No. 1, which will serve to determine the action of the cerealine.
The bran should now be washed until the water issues pure, and until it shows no bluish color when iodized water and sulphuric acid are added; when the washing is finished the bran swollen by the water is placed under a press, and the liquid extracted is placed, after being filtered, in a test tube. This test tube serves to show that all cerealine has been removed from the blades of the tissue. Finally, these small blades of bran, washed and pressed, are cast, with 50 grammes of lukewarm water, into a test tube, marked No. 3; 100 grammes of diluted starch to one-tenth of dry starch are then added in each test tube, and they are put into a water bath at a temperature of 104° Fahrenheit, being stirred lightly every fifteen minutes. At the expiration of an hour, or at the most an hour and a half, No. 1 glass no longer contains any starch, as it has been converted into dextrine and glucose by the cerealine, and the iodized water only produces a purple color. No. 2 glass, with the same addition, produces a bluish color, and preserves the starch intact, which proves that the bran was well freed from the cerealine contained. No. 3 glass, like No. 1, shows a purple coloring, and the liquid only contains, in place of the starch, dextrine and glucose, i. e, the tissue has had the same action as the cerealine deprived of the tissue, and the cerealine as the tissue freed from cerealine. The same membrane rewashed can again transform the diluted starch several times. This action is due to the presence of the embryous membrane, for after four consecutive operations it still preserves its original weight. As regards the remains of the other segments, they have no influence on this phenomenon, for the coating Nos. 2, 3, 4, and 5, separated by the water and friction, have no action whatever on the diluted starch. Besides its action through its presence, which is immediate, the embryous membrane may also act as a ferment, active only after a development, varying in duration according to the conditions of temperature and the presence or absence of ferments in acting.
I make a distinction here as is seen, between the action through being present, and the action of real ferments, but it is not my intention to approve or disapprove of the different opinions expressed on this subject. I make use of these expressions only to explain more clearly the phenomena I have to speak of, for it is our duty to bear in mind that the real ferments only act after a longer or shorter period of development, while, on the other hand, the effects through presence are immediate.
I now return to the embryous membrane. Various causes increase or decrease the action of this tissue, but it may be said in general that all the agents that kill the embryous membrane will also kill the cerealine. This was the reason why I at first attributed the production of dark bread exclusively to the latter ferment, but it was easy to observe that during the baking, decompositions resulted at over 158° Fah., while the cerealine was still coagulated, and that bread containing bran, submitted to 212° of heat, became liquefied in water at 104°. It was now easy to determine that dark flours, from which the cerealine had been removed by repeated washings, still produced dark bread. It was at this time, in remembering my experiences with organic bodies, I determined the properties of the insoluble tissue, deprived of the soluble cerealine, with analogous properties, but distinguished not alone by its solid organization and state of insolubility, but also by its resistance to heat, which acts as on yeast. There exists, in reality, I repeat, a resemblance between the embryous membrane and the yeast; they have the same immediate composition; they are destroyed by the same poisons, deadened by the same temperatures, annihilated by the same agents, propagated in an analogous manner, and it might be said that the organic tissues endowed with life are only an agglomeration of fixed cells of ferments. At all events, when the blades of the embryous membrane, prepared as already stated, are exposed to a water bath at 212°, this tissue, in contact with the diluted starch, produces the same decomposition; the contact, however, should continue two or three hours in place of one. If, instead of placing these membranes in the water bath, they are enveloped in two pounds of dough, and this dough put in the oven, after the baking the washed membranes produce the same results, which especially proves that this membrane can support a temperature of 212° Fah. without disorganization. We shall refer to this property in speaking of the phenomena of panification.