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Show lOG ON CLA SIFICA'l'I N. I have italici eel to look into th n1att r afr h, I have found that the assertions 1na 1 th r in r p ting th' pia uta of tho Hat are as compl tely contrary to fa 't as ar th r p cting the brain of the apes which I have already it d fron1 th mne anthor. }'igure 42 repres nts a section of th nt ru , horion, and partially-inj ct cl pla nta f a :C tal l~at, one inch and a quarter long, taken in a dire ·tion p rp ndicular to the long axis of tb ut rin ornu. a i th n1 01n tJ·iurn traver d by a large uterine v in; b is th wall of th ut rns becoming looser in t "xture an l trav r "' 'd Ly hug v •n us chanuel8 in its inn r substance, c; d i ~t d i lual layer of the nt ru, of a ·ctV rnous tructur , ' h n \ a cnlar pro continued toward the ·horionic 1nfac of th pla onta. A lara vein (i) pa ses dir ctly fr 1n th l iclual lay r (d), aucl tho uterine sinu es bcn0ath it, t n ar th I ciwri ni I •nrfae or tho placenta, b neath whi h it bran h on h >rizontally. Th ('horion (f), render cl va ular v r it n n-rla · nt:. l part by the omphalom seraic v Is (k), only l1 .)o·in. to ... hi bit villon , processes and fold at th p int (g). Th ut nn t villi appear to n1c t b fr ; but n1 r rnall r, th y b como closely c nn ct l " ·ith th ' upp r 'tufa f th ' pin nta; and over th c ntral thir l of th f tal fa f th' pla · ntn., the nmLilical v · cl (l) rmnify iu a ra 1iatin · fa hi n, and , ncl }Jrolongations ZONULAH, DIRCOIDAI.J, AND DII!"FU E PLACENTJE. 107 Jown betwc n the decidual lam 11(. • The ·lightc ·t tnt ti n exerted upon the cord causes the placenta t scparat al ng th line e, m, rn, e, bringing with it, of cour. , the up- hapcd decidua, d.* It is obvious, fr01n the above description, that the " p dun-culatc and cotyloid" placenta of th I at do s not '' con i t of frotal parts exclusively," but that, on th ontrary, a Eschricht has so well pointed out, "the organic int rLlending of the circulatory organs of mother and off: pring " i a c mplete in the Rat as in Man ; and that, there£ re, the oncludin o· paragraph of the citation from Professor Owen's paper ught to be reversed. The Carnivora develop a well-marked decidua, and th ir * My friend Professor Rolloston has made the following stat m nis in a pap r · which will shortly appear in tho Zoological oci ty's Tntn actions. I. 'fho ·nat's afterbirth con ists of a sauccr-shap cl d cicluous s rotina,, and a button-shaped placenta proper. Afterbirths made UJ of th s two lemont may bo found in the stomachs of animals of this spcci s after parturition, a th y, lil ~ many other Mammals below tho Simiudw, devour them. Uul r th so circumstances, tho two constituent fn.ctors of tho afterbirth 'may eith 'I' bo found in their normal connection, or they may bo separated one from tho other. 2. rrho non-deciduous part of tho scrotina forms in tho Rn.t, after parturition, a hernial protrusion i~to tho mesometrium, which ha been mi~takcu for a dcv loping ovum (sco lluntenan Ou,talogue, Phys. Scr. Prep. 34GG); ju-t as tho homoloO'ous ·tructures in tho human subject form a hernial protrusion into the avity of the uterus, which may persist as a more or 1 s elevated area for several years. (Of. Hobin, Mom. Imp. Acad. Mod., tom. xxv., p. 137.) 3. 'fhc homologue of tho saucer-shaped deciduous scrotina of the Rat is, in the human sub~ ct, tho thi~ layer of la.minated albuminous tissue, which, in a placenta ?xpcllcd w1tho~t suffcrmg much vwlcnco, is soon clothing its uterine surface. It IS smaller, relatively, to the other structures concerned in the nutrition of the frotu in the human than in any other species. It is more easily demonstrable in th~ Monkey (Macacu~ Nemestrintts,. c. g.), as being a more coherent and stouter membrane than m Man. It Is, however, h ro still a condensed and membranous structure, as compared with its pulpy homologu sin Carniv01·a Insectivora and Rodents. ' ' 4: In early p~riod~ of ut ro-gcstation in the common Shrew and lledgchog, tho de~tdu?us s.crotma lS a very much larger structure than the placenta proper wlucl~ It entirely covers, except on the footal aspect. But iu the Tenrcc ncar th~ full t1me, tho decidua se1'otina is of but wafer-thickness. ' 5. Dr. M:~tthcws Duucan and M. Robin have shown that the mu ular coat of the u~cl'lls. ~s never left . d nuJ.cd after parturition in tho human ubj ct. The same 10mml\. 11olds good m tho case of the "u c1'cl11'"'to " 11"" z · · 11 f 1 · r • ,. ..Lr.tamrna la, lU a 0. w ll h ,t mor~ ?r los mochficd mucous tissu , tho "nou-d cicluous serotina ., is left aft r prtunttOn, upon the utero-placental area, from wJtich the clcciduot;s s rotin~ and P aconta proper luwe been separated as "afterbirth.'' |