Before we part, however, I must apologize for something. I have not described to you what the bile consists of, or what kind of refuse the blood leaves in the liver; nevertheless, as you take an interest in this much-neglected book of nature, you ought to know these things.
It is, however, very difficult to lead you by the hand through so many wonder*, where the secrets of nature are all in operation at once, and to explain each as soon as we meet with it. They combine, and progress together like the waves of the sea, where one breath suffices to agitate the whole mass.
When we have talked about the lungs, we will have another word to say about the liver.
LETTER XII. THE CHYLE.
To-day we have to begin by making acquaintance with a new term. I would willingly have spared you this, if I could, for the word is neither a pretty, nor a well-chosen one, but we cannot get on without it.
You are aware now that the learned, unknown sponsors, who gave names to the different parts of the body, bestowed the odd-enough one of chyme on that pasty substance which passes out of the stomach when the cooking is over. We have said quite enough about it, and you know enough of it I am sure. Well! the people seem to have had quite a fancy for the word chyme, for they adopted it again, with only a very slight alteration, when they wanted to specify separately the quintessence of the chyme (the useful part that is), which has to unite with the blood, and which we have been speaking of as the gold of the aliments—this then they called chyle. I give you the name as I received it, but have no responsibility in the matter.
In concluding the last chapter I said we were sure to find there was a plan for extracting the best part of the chyme, viz. the chyle, from the intestinal canal; and a very simple one it is. A complete regiment of those little scavengers lately described, are drawn up in battle-array along the whole length of the small intestine, but especially round about the duodenum. There, a thousand minute pipes pierce in all directions through the coat of the intestine, and suck, like so many constantly open mouths, the drops of chyle as fast as they are formed. They are called chyliferous vessels or chyle-bearers, just as we might call hot-air stoves caloriferous or heat-bearers—from the Latin word fero, which means to carry or bear. I mentioned before that there were, within the intestine, certain elastic valves which obstruct the progress of the chyme, and oblige it to be constantly stopping. There are in fact so many of these, and the skin which lines the intestinal canal is so folded and plaited, that if it were stretched out at full length on a big table, it would cover at least as large a surface as that other skin, with which you are so well acquainted, which entirely clothes the body outside.
Now, the chyliferous vessels we have been speaking of insinuate themselves into all the plaits and folds alluded to, and thus they reach at last the very centre of the chymous paste, and not a single drop of chyle can escape them. They do their work so well, that the separation is effected long before the paste reaches the large intestine; and when that has forced its way through the door which guards the entrance, and which prevents its ever returning again, the chyle is already far off on its mission. It has threaded its way along the little pipes, and, always creeping nearer and nearer, is on the high-road to the heart, where it is anxiously expected.
And what becomes of the rest? There is nothing further to be said about it, but that it shares the fate of everything else which, having answered its purpose in its place, is no longer wanted and must be got rid of. Thus in works where iron-stone smelting is carried on, the refuse that remains after the ore is extracted, though available for road-making or other purposes, is thrown out of the manufactory as a useless incumbrance there.
Our history requires us to follow the fate of that golden aliment the chyle, which is now in a condition to support the life of the body, and every drop of which will turn into blood—the blood which beats at our hearts, nourishes our limbs, and sets at work the fibres of our brain.