A Discourse Concerning Digestion in a Letter to the Publisher from Mr. Charles Leigh of Brasen-Nose Colledge Oxford

A Discourse concerning Digestion in a Letter to the Publisher from Mr. Charles Leigh of Brasen-Nose Colledge Oxford. SIR, Should I reckon up here the many controverted hypotheses of Anatomists concerning this subject, & let up a new one of my own; it might perhaps seem a piece of fond presumption: I shall not therefore be so vainly opinionative as to think that I have here fully explained the nature of Chylification, but shall onely give you an account of an Artificial digester which I hope may something illustrate the naturall one. It has been observ'd by He'mont, Mebius, Tachenius, and the Honourable Mr. Boyle, that meats by being kept in an acid liquor, would looke extreamly white. But I doe not find that by the help of a salt that is meerly an acid, there can be any chyle prepared from any meats. Wedelius is of opinion that Chyle is nothing but a mixture of oil and Serum. Tilingius affirms that tis made by a nitrous Salt. Dr. Harvey by trituration. Dr. Willis by an acid and Sulphur. Diemerbrook and Sylvius by the Saliva. Dr. Mayow by a Nitroaerial principle. Galen and Aristotle by heat. Others by a ferment spewed from the glands in the bottom of the Stomach. Others by the relics of the meat grown sour. So many different opinions I shall neither pretend to reconcile or decide. And shall therefore onely lay down the Phaenomena which this liquor afforded, and from them draw inferences as probable conjectures. But shall in the first place premise a description of this digesting liquor, and see how far it may probably parallel the naturall ferment in the Stomach. The taste of it is like meat vomited out of a full stomach, something Sour, but will not ferment with an Alkali. It is prepared from spirit of Sulphur, spirit of Hartshorn, the the Chyle of a Dog and the Saliva: it is pellucid and without any smell: the Salt that it shoots into is cubical. Upon veal it afforded these Phenomena. Into a dram of this liquor I put a piece of veal about the bigness of a Nut, & set it upon a digesting furnace. In two hours time there came from the meat a liquor that had the colour and taste of Chyle, and the meat afterwards was lighter, dry, and insipid. And it afforded the same Phenomena also in beef, mutton, or any other meat that I could meet with. And here it is to be noted, that tho it has been affirm'd by some that the same thing may be done by acid liquors only, yet since by all the tryals I have made upon 'em, I have not yet observ'd the like Phenomena, I hope my Scepticism in this case may be pardonable. If therefore we now consider that by the help of this menstruum there came from the before mentioned meats, a liquor which had the colour and taste of Chyle, and if we further consider that the taste of this menstruum is not distinguishable from the taste which is perceivable in meats vomited out of a full stomach; I hope I may without being thought fond of an Hypothesis, conjecture that by some such menstruum the meat is digested in the stomach. But here I would not be thought to affirm that by a liquid menstruum alone the meats are digested, but that there are likewise required these further requisits, in some, or in most creatures. First, that the stomach receive a gentle heat from the liver. 'Tis therefore for this reason said by the Learned Glisson, Calor hepatis in hepate est actio, & ventriculo est usui. Secondly, that the stomach have a natural situation. For, says Riolanus, Interdum ventriculus propendet usque ad umbilicum, ut observatum in cadaveribus, quod vita coctioni multum immoderat. And Vesalius in his Anatomy Lib. 4. gives us this example. Observavi omentum in scrotum devolutum & autum ventriculum ex sede sua distraxisse, adeo ut munus ejus desiceret. Thirdly, it is afflited by the omentum. This may be argued from those creatures which have no caul, helping concoction by doubling their hinder legs, and resting their bellies upon them, as hares and conies. A second instance may be brought from Valentinus. Andreas Molenbrochius in Miscellaneis curiosis Ann. 1670. Militaris quidam vir dum vivaret nil nisi ventriculum accussabat, quod nullum cibum appeteret coqueretque, cui ad comfortandum ventriculum multa exhibita fuere sed omnia incassum: dissecto cadavere, omentum plane putrefactum est, ventriculo reliquisque visceribus salvis; ex quo colligitur, omentum adventriculi coctionem non parum facere. Fourthly, 'tis necessary that the stomack have a Tunica villosa: 1. Because that by that it is enabled to divide the meat into parcels, which undoubtedly must much facilitate the operation of the natural ferment: As we see all menstruum will sooner dissolve metalls when they are filed into parcels, than when they continue in the lump. 2. If it had not a Tunica villosa, the Tunica carnea would be apt to be too much distended by our meat and drink, which would necessarily weaken the tonical motion of the stomack, and consequently therefore its digestion. Fifthly, that there be a right digestion, it's necessary that there be windings of the Intestines; for if it were not for these, the digested meat would move too fast from the stomack, and so torment us with perpetuall hunger. Which assertion I think may sufficiently be confirm'd by these two instances. The first is from Cabrollius observation the 10th, and Riolanus Anthrop. lib. 2. cap. Firminus Chaudonius voracitate erat Erysichtonea, cui causam praebuit, quod nec stomachi nec intestinorum figuram ullam habebat proportionatam, unicum à Pylori loco ad Anum Intestinum erat sine ullo anfractu, cumque aliorum Intestina quatuordecim quant ulnas, hujus vix ad quatuor spitthamas accedebant in formam literae S. The 2. Instance is taken from a creature in Lithuania and Muscovy that generally feeds upon it's prey, till it's belly be twell'd like a bladder, then conveys it self to some strait place, and so violently forces forces the meat out of its stomach and intestines, and then immediately returns to its prey with as craving an appetite as before: which continual and insatiable hunger is judged to proceed from the straitness of its Intestines; for, as the Learned Pamius observed in its dissection, its guts had no circumvolutions or windings. From these therefore 'tis plain that besides a fermenting liquor in the stomach other external means concur to digestion. I shall therefore in the last place inquire what may probably be the Ingredients of the natural ferment, & so conclude. The Ingredients of the natural ferment I take to be these. The saliva, the succus of the Glands of the stomach, and a nitro-aereal spirit of the nerves. That the Saliva is an ingredient, may seem probable from these reasons. 1. Because that by the help of this, meats tho impregnated with different principles, may be made to mix with a menstruum; for, as the Learned Steno has it pag. the 27th, de glandulis oris: Saliva vero omnia ferre valet; sive intra corpus sive extra corpus examinaveris, nihil invenies quod illa respuet, nihil cui sine pugna non associetur. 2. Since the Saliva is impregnated with a volatile salt, it is probable that that too may help digestion. The second ingredient I take to be a liquor that is separated by the glands in the bottom of the stomach. And this I shall evince by the Authority of the famous Willis, and Sylvius De le Boe. And first from Dr. Willis in his Pharmaceutice Rationalis, pag.6. Tunica hæc villosa in postica sive convexa ejus superficie, qua tunicæ nerveæ cohaeret, glandulis annulatis numerosissimis ubique consta est, qua proculdubio vasorum in tunica nervea dehiscentium ora contegunt: ac (uti videtur) humorem illis destinatum aut ab vis depositum, immediatius excipiunt ac percolant. Sylvius pag 881. gives us this account of it: hoc chylificans fermentum in recens natorum vitulorum ventriculis reperitur crassiusculum, diciturque coagulum: senem autem minuitur, ac in adultis, glutinis instar, offenditur liquidiusculum inter ventriculi rugas hærens. By these there- fore it seems probable, that the glands in the tunica villosa separate a fermenting liquor, and 'tis further observed that those creatures which have the most of these glands, are the most voracious. Lastly that the nitro-aerial spirits of the nerves are an ingredient of the stomachical ferment, seems reasonable from the Arguments of Dr. Mayow, pag. 55. He argues thus: Jam vero cum piritus animales e partibus nitro-aereis constant, haud difficile erit intellectu quomodo effectus praediti ab eisdem in ventriculo perficiuntur. Quanquam enim spiritus Nitro-aereus acidus non est, ab eisdem tamen ferrum corroditur, vitriola perficiantur, salia fixa ad fluorem perducuntur, rerumque compages tanquam ab universali mensuro solvuntur. These therefore (Sir) are my thoughts concerning digestion; but here is nothing in these dogmatically asserted. If therefore any Hypothesis here may be found erroneous, upon better grounds I shall readily lay it down. I am, SIR, Your very humble Servant, C. L.