INCITBATION. 



a piece of ice oF the ihicknefs of a linger extended from the which reafon it appears Iffs than it did when the chick iv.-- 



congealed amnios into the mouth of the foetus, and down the fmall. Tlie quantity of the liquor amnii ?t any given tin,;, 



cefophagus as far as the Iloinacii. even admitting that it is not fecrcted by the fetus, wonit: 



There have been fometimes feen alfo in the ftomach of be quite infufficient for the formation of the latter, 'lit 



the fatal calf' the fame kind of fatty concretions, that ufu- principal part of this fluid alfo is loft wlicn the membran- 



ally exift in the amnios of this animal. The hairs of the that contains it is ruptured, previous to the liberation of the 



calf have been difcovered in tlie meconium. New-born in- young animal from the uterus or the egg. We fhould, on ali 



fants have been obferved to vomit a iluid refembling the thefe grounds, deny that the liquor amnii is deftined to fuftair. 



liquor amnii. the foitus in any circumftances. 



It has been remarked by Harvey, Huller, :<nd feveral other In all oviparous animals, there is no necefiity for fuppofin .; 



writers upon incubation, that tlie fcctal chick frequently the liquor amnii to l)e a nutritive fluid, as there are oth.: 



opens and fliuts its mouth while incloied in the amnios, as if humours provided for the purpofe of nouriihing the foetu- 



it were performing the act of fwailowmg. The fources of nutriment, during fostal life, are particulai- 



The preceding tadts leaw-. no doubt that the water of the evidentin the ovum of birds. 

 amnios pall'cs into the ftomach of the foetus, but by no In the hiftory of incubation it will be found, that l' 



means proves that it contributes to tlie nouriiliment of the albumen begins to diminiih as foon as the fcetus become;; ; 



young animal, but i-alher the contrary, as if it were either parent, that it continues to decreafe regularly as the clr 



digefted in the ftomach, or confumtd by abforption, it grows, and that this fluid is entirely confumed at the end i 



eould not be found towards the end of geltation, or after- incubation : there is, therefore, no doubt that the white 



birth, in the quantity reported. the egc is the fubiiance from which the chick is form 



Thofewho give credit to the nutrition of the foetus by It has been fuppofed by fome writers, that the yolk :- 



the hquor amnii, cite fome remarkable cafes in wiiicli the contributes to the fnpport of the chick while in the e, 



umbihcal cord is faid to have been deftroyed before birth, This opinion refts cliiufly upon the circumftance of the y • 



or in which the infant has been born with the cicatrix at becoming larger and more fluid after the while begin? 



the urabihcus pcrfcdfly formed. See Obferv. rarior cent diminifli, which has been attributed to the albumen pall 



poft pars I. obf. 32. — Journal des favans, annce 1673, into it, that the two fluids might be mi.scd together, ai-a 



p. 69. Obiervat. communiq. par Chn.tton.— F. Hoffmann & afterwards converted into the fubftance of the chick. Mai- 



Triller Didert. de pinguid e fucco nutr. fuperfl. p. 10. and tre Jan, I.pvpille, and others believed, that the white is ab- 



Rommel Ephemer. nat. cur. die. 2 "a 7, obf. 209. forbcd h- •' ■ ,'■ ' ■ -. t -? ''•■•? conveyed into the yolk-bag. 



It fliould be remarked, that of thefe obfervations, fome and Lf < ' to demon ftrate the tubular 



are related in a manner which makes their accuracy very ftruftti;.' We have already ftated, 



doubtful; and otliers, even if corredtly ftated, do not that by 11 - ij 1 we could not perceive the 



prove the point they are propofed to eftabhih. Thus ftrufture d<:i;:iihed by Lcvc.iie ; ue arc therefore led to goi|- 



the infant with the cicatrized navel was not feen by Chat- elude, that the fluidity of the yolk, during incubation, is oc- 



ton until five months after birth ; and in fome of the cafes cafioned by the organization of that humour undergoing a 



where the cord was faid to be injured or putrid while the change fi-om the application of heat. We have found alfo 



child was alive, it does not appear that the circulation had the yolk become fluid when eggs were fat upon, which had 



been deftroyed. not been fecundated by the cock, and in which the white 



We ihould not have noticed the doftrine of the nutrition vi'as not fenlibly diminiflicd. The wei^jht of die yolk at 



of the ftetus from ihe liquor amnii, as it is generally dif- the end of incubation, almoft proves that it is not concerned 

 credited, had it not been advanced with foine limitation by in the ncurifliment of tlie chick, until after the animal is 



.Lobltein in a modern publication. This author does not excluded from the egg, 



pretend that the foetus fwallows the liquor amnii, he allows We canfefs, huweur, that we are unable to form a decided 

 that the young animal exills and increafes in growth, before opinion with refpeft to the manner in which the albumen is 



the digeftive organs or even the mouth are formed. He is carried into the body of the chick. Throughout incuba- 

 alfo aware, that there have been monfters produced in whom tion the white tends to the lower and fmall end of the egg ; 

 the head was w^anting. He therefore fuppofts, that the the chick is placed at the upper and grctit end. There is, 

 fluid of the amnios is taken into the body of the foetus by therefore, no diredi communication between tlie chick and 

 the abforbents of the flvin, which opinion he grounds upon the albumen. The blood-veirds of the egg have apparently 

 the following circumftances : Many of the cold-blooded ani- no immediate conneaion with the white, until its proper 

 mals, he fays, have no placenta, but in every fpecies the membrane is formed, at uhicii time this humcwir is already 

 foetus floats in a clear liquor, analogous to that of the amnios, much reduced, and even then there are only a few wander- 

 Tliis fluid, he remarks, diminiflies in proportion to the growth ing vefli^ls fpread over its membrane. Thefe fafts afford 

 of the foetus ; it likewife remains uncorrupted during foetal reafon for the fuppofition that the white pafles into the yolk- 

 life, which fact, he thinks, can only be explained by its bag, through the chalazse ; but, on the other hand, it is 

 pafling fucceflively into the body of the young animal, fcarcely credible that the white, after being mixed with the 

 (Lobltein fur la Nutrition du Pectus, § 88.) Our reply to yolk, (hould alone be abforbed during incubation, and the 

 this reafoning would be, that the liquor amnii is not a nu- latter fluid left undiminiflied. 



tritive fluid perhaps in any inftance ; that when lirll perceived. The chalazoj, v.-licther they perform the office of abfor- 



it is in a very fmall quantity : it is, in the higher clalfes of bents or not, aft as ligaments to the yolk-bag, and have the 



animals, contained in a membrane which is continuous with cffcft of keeping, throughout incubation, that furface of the 



the ll<in of the foetus, and which membrane further derives its bag uppermoft on which the chick is iituated, in order that 



blood-vefl'els from the foetus. It is, tiierefore, a fecretion of it may receive heat from the hen. See Ecu;, 



the young animal. During feveral days of incubation it The ufe of the veficula umbilicalis isa fubjtd on which no 



increafes as the chick grows, and in the latter periods does fatisfaftory theory has been yet made out. 



net perhaps aftually diminifh in quantity, but ceafes to in- The older anatomifts fuppofed tliis part to be a refervoir 



creafe in proportion to the developemeut of the chick ; for of urme, a.^d gave it the name of allantoii. Lobftein conli- 



ders 



