A Letter Written to the Publisher by the Learned Mr. Ray, Containing Some Considerations on the...

A Letter Written to the Publisher by the Learned Mr. Ray, Containing Some Considerationson the Conjecture in Numb. 114. of These Tracts, about the Swiming Bladders in FishesAuthor(s): John RaySource: Philosophical Transactions (1665-1678), Vol. 10 (1675), pp. 349-351Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/101654 .

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( 349 )

A Letter written to the Peblijher by the Learned Mr. R ay, containing fome Con- fiderations on the Conjedure in Numb. 114. of tbee Tratis, about the fwzimn ing Bladders in Fifher.

This Letter is not mentioned in the Contents , bec'auf it vs;

thought at the time when the firfiheet ww i aprinting, i/ie

Difcourfe about the precedent In/Irgment wonld hbve ta ken up all the room of this Tr4a.

SI R, was much plea'fed and fatisfied with the ingenious con)ct6ure I found in your Tranfailiovs of May laft, paI. 3 oxconcern-

ing the fwimming Bladders of FiCfhes; and perfwade mny fe f that the Author thereof hath hit upon their true ufe, viz. to fuftain or keep them up in any depth of water. For i.itha:hl been obfervod by fome, and I find it in Mr. Wil(lughLyes general notes of Fifhies, that if the fw7inmming bladder of any Fifhi be pricked or broken , fuch a Fifh (inks prefeitly to the bottom.i, and cai neither fupport nor raife up it Tlf in the w,ater. 2. Flat Fifhes, as Soles, Plaife, &c. which tie alwails grovelingat the bottom, have no fwimming b-adders that I could ever find. 3. In moft Fifhes there is a manifeft channel leading from the gullet or upper orifice of the ftomach to the Laid bladder,vhich without doubt ferves for conveying air thereinto, as may ea- fi y be tried by any one that plea res. But though air may be i-ceived into the bladder, yet is there a value or Lowle other contrivance to hinder the egrefs of it- for you fball fooner break the bladder than force any air out by this channel. Ye: in Sturgeons Mr. Wdllughby lath obferved, that prtfflng the

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(3O to) Lhadckr,the fLoiomach preFently ('welled : So thiat it feenms in t]hat Pit ih the air paffes free'ly both wayes. Po(ffblv, the Fith whil,e aLive may have ani abil.ity to raife up thi~ valve, and let out a.:r upon occafion ,which yet I doubt of, becaufe other A.- riimials have no ('uch faculty of opening any valves made to ltop tihe reflux of fluids. But I verily think , there, is in the coat of this bladder a mDu(culous3 power to contra& it when the Fifli li'fts -For, in imany Fifhes it is very chick and opake, like the coat of an Artery ( which lha~h as Dr. WiUis ob('erves, fuch a

uf'cular faculty ) as for example in all the Cod-kind; in fome., VIg. the Hake, called in Lat.in MerIuciAui4 it is inwardly covered width a red carneous ('ubhiance, which I take to be nmuf- Cuou flefh ; in othere,it is. forked at the top, and to each horn hath a tnu(cle affixed. Now the mufculous force need not be g-eat, being kill affWfed by the water as the Fith defcends; the prefiiLire of the water being, miuch greater at the bottomi than at thep top , as appear-s by the afcending bubble. But whereas it, is f'aid, Perhaps the Filfh can by its ('ides or forme other defence keep off the pre fureof the% v,~ater, and give the air leave to di- late it ('elf : Jt- m-ay be ob)dhIed , if it can do fo, what needs then any air-bUadder ? the cavity Of the a'd omen may ferve tbe turn. To which f anf'wer , that this power of'dilating the at,- domenby the niufcles may aflift Fithes to rife, whofe natural pl'ace is towardi the bottomi; and the Air compreffed in the bladder- dilating it ('elf as the Fifh] afcends , facilitates the a- ction of th-e muFcles. But thofe Fifhes that defcend by con. tra&ing the bladder,lecting the conitra(lingmufc1eceafe to a&, will riFe again of their own accord , the Airf within dillating it ('elf, as we ('ee in glafs bubbles by comprelTi'on of the Air in them defcending , which as foon as the force is rem-oved af- cend without more ado. Lefides the flat Fifhies I before mnentioned , all the carcilagineous kind, as well fiat as long, wvant ('xNi,Mming bladders:- What courfe they ufe to afcend and dtefcenc in the: water, I know,, not. Many of the Eel4Iind (not all) have ('wimniring bladders; yet can they hardly raife

chemfel-ves in the water, by reafon of the-length and weight of their tails:- I fuppore, the Air-bladder being nerar their

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( 35r ) heads helps them to lift up their head and fore-part; Great diverfity there is of fwimming bladders in refpe& of figure, fubftance, fituation and connexion in feveral Fifies: But not being able to give you any reafonable account of each , I hfal I forbear to add any thing further of them.

S IR,

Tour very humble Servant

NiJ4d/1et n, June 22, 1675.

John Ray.

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