March 31, 1882.] 



♦ KNOWLEDGE 



477 



COD-SOUNDS AND SCIENTIFIC PRIVILEGE. 



WHEN' I stated (page 295) that the tough leathery membrane 

 of tlio cod-fish, known to epicnres as the " sound," is an 

 organ of different structure and anatomical relation to the swim- 

 bladder of other fishes, 1 had no idea that the subject was suffi- 

 ciently interestinjr to call forth the critical correspondence it has 

 elicited, and should hardly have prolonged the discussion, but that 

 another and far more important subject has been connected with 

 it. "Old Kossil " says (page 380), that I have illustrated " the old 

 saying that a cobbler should stick to his last," ami that on " pass- 

 ing into the domain of the biologist " I must " bo regarded as an 

 intruder." Dr. Wilson (page 129) quotes and supports this state- 

 ment which assumes that scientific inquiry, scientific discussion, or 

 scientific criticism is the exclusive privilege of labelled specialists, 

 who must never invade each others' domains. 



This is a mischievous dogma, too often assorted with less cour- 

 tesy than by the gentlemen above-named, and sometimes even 

 with downright insolence by certain narrow-minded pedanta. 

 "There is no man old enough to be an expert in all the sciences, 

 and yet all the sciences are but one science, and all our subdivisions 

 ore mei-ely artificial devices for the convenience of study. Hence, 

 if every man confined himself to his own particular branch of 

 special knowledge, the divine unity of creation would remain 

 unknown, and the highest object of all science — the uplifting and 

 purification of the human mind by the unselfish contemplation of 

 the marvellous harmonies of the universe — would bo unfulfilled. 

 The new-bom science of celestial chemistry could not have come 

 into existence without the previous wedding of tho laboratory to 

 the observatory ; and if we take a general survey of the progress 

 of human knowledge during the present generation, it will be seen 

 that the greatest strides have been made by those who have boldly 

 stepped across the'conventional boundaries that mark the customary 

 subdivisions of the sciences." I wrote the above protest thirteen 

 years ago ; 1 now repeat it with especial emphasis in the columns 

 of KNoni.EriGE, the value of which I regard as largely due to its 

 general freedom from the pedantry of the self-sufficient specialist. 



Has not Tyndall invaded the domain of the biologist in conduct- 

 ing his researches on atmospheric germs, and have not the truly 

 philopophical biologists good reason to thank him for doing so ? All 

 such biologists acknowledge the importance of Herbert Spencer's 

 profound contributions to the theory of evolution ; but can he be 

 labelled a biologist ? I need only mention the names, of Humboldt, 

 Bunsen, Kirchoff, Helmholtz, Huggins, Huxley, &c., as illustrations 

 of men who, by forsaking their special lasts, have ceased to be 

 scientific cobblers, and have thereby become true philosophers. 

 This very magazine could have had no existence had its editor sub- 

 mitted to be strapped doivn to the astronomical last with which 

 his earlier literary efforts are associated, and some of his best essays 

 must have been suppressed had he not invaded other " domains." 



Such specialists are unquestionably necessary to the building up 

 of the glorious edifice of inductive science, just as special masons, 

 bricklayers, carpenter.*, joiners, Ac, are demanded for physical 

 buildings, and I should bo the last to dispute their dignity and 

 importance, even when protesting against their undue assumptions 

 of exclusive privilege. 



Dr. Wilson and " Old Fossil " are quite right in asserting that I 

 am not a biologist, thongh my earliest studies were biological, and 

 date from a period preceding the invention of the term " biology " 

 and tho birth of Dr. Wilson, viz., 1841, when I was a pupil of 

 Professor Jamieson in " Natural Histoiy," and attended the lec- 

 tures of "Monro terlitis" on " Anatomy and Physiology" in the 

 University of Edinburgh. 



"Old Fossil " tells us that he dissected a cod-fish of 8 or 91b. 

 weight on tho day of writing. I hd,ve dissected many twenty-five 

 to thirty years ago, and therefore depend upon memory. The 

 reader, however, may judge for himself, by simply cutting such a 

 fish in half, or asking a fishmonger to do so for him, and he will 

 then be able to judge by the diameter of the blood-clot enclosed by 

 the stout membrane in question whether it can possibly bo con- 

 tained within an aort.a of -r-th of an inch diameter. If the section 

 is made at about the posterior termination of the abdominal cavity, 

 he will find that this blood-clot is nearly half-an-inch in diameter, 

 and confined between the spines and the thick membrane in ques- 

 tion. If he follows this membrane forward, he will find it still 

 adherent throughout its whole length to tho spines, and uuder- 

 lapping the blood-clot, which now becomes divided, and lies on 

 each side of the body of the vertebra?, accumulated in tho hollows 

 formed by the bases of the vertebral arches. It also contains air, 

 and this has probably led " Old Fossil " to suppose that it is a true 

 swim-bladder, the organ which modern biologists regard as an 

 homologue to the lung-bag of the amphibia and reptiles ; one of Dr. 

 Wilson's " found links." 



All such bladders differ essentially in structure and anatomical 



relations from the cod-sound. They are formed of a thin, trans- 

 lucent, delicate membrane, corresponding to the pleura, or mem- 

 branous envelope of the lung-ljag of air-breathers ; the cod-sound 

 has a tough leathery coat, like that of our own arteries. It is a 

 contradiction to all anatomical analogies to suppose that a mere 

 air vesicle should have walls strong enough for a fire-hose. The 

 true air-bladders, like the lung-baga of the amphibia, are, as 

 John Marshall says, " off-shoots from the upper part of tho 

 digestive canal," and come away freely from the abdominal 

 cavity along with tho other viscera when these arc removed. 

 The cod-sound is connected with the heart (as a )n-olonga- 

 tion or modification of the hulbus arteHosus) cf tho fish, and 

 so firmly attached by its edges that it has to be forcibly torn or 

 " sondert," by the Norsk fishermen, after all the rest of tho viscera 

 are removed, and thus, as I believe, obtains its name. When not 

 thus sundered for salting, it is ripped open in order to remove the 

 blood which it contains throughout its entire length. I have ex- 

 amined the swim bladder of many fishes — the single-lobed bladder 

 of our common fresh-water fishes ; the slippery double bladder of 

 eels ; the curious three-lobed blaildcr of the gurnets (tho pro- 

 portionate capacity of which is at least twenty times that of a cod- 

 sound, and yet is composed of thin membrane) ; and the still more 

 delicate, collapsing bladders of the herring and other similar fishes 

 — but have never found any blood within them, still less that they 

 enclose the great dorsal clot which I find in all fishes after death 

 enclosed in a special membrane corresponding to the cod-sound, 

 though generally thinner, and always quite independent of the swim 

 bladder. 



In spite of the scalpel of " Old Fossil," I still regard tho sound 

 of the cod-fish, and the corresponding membrane of other fishes 

 similarly adherent to the spine, as the main bloodvessel of the 

 animal, for the simple reason that its blood is always contained 

 therein, but I do not deny that the air which it also contains may 

 assist the buoyancy of the fish, seeing that this buoyancy is 

 obtained in other fishes by other aiTangements than that of the 

 ordinary lung-like swim-bladder. 



As regards the contents of this dorsal aorta during life, I may 

 mention one experiment. I have on several occasions lashed myself 

 to the martingale of a schooner sailing in the Mediterranean, and 

 stood so near to the water that my feet have dipped when the vessel 

 pitched. From this favourable position I have speared bonettas, 

 and observed that when one of the five barbs of tho "grains" (as 

 the sailor calls the murderous implement), has pierced the adherent 

 membrane in question, that the water all around the fish has 

 suddenly become deeply stained with blood to a distance of a foot 

 or eighteen inches, and the usual blood-clot under tho spine has 

 diminished accordingly, indicating more contractilo work than could 

 be done by the tiny heart attached to the gills, and suggesting the 

 probability of direct and powerful contraction of this sub-dorsal 

 membrane, which I believe does much more in circulating tho blood 

 through the body of fishes than Dr. Wilson and " Old Fossil " 

 imagine. Eymer Jones (who was a biologist especially strong in 

 comparative anatomy) tells us that there is " no systemic heart in 

 fishes, the aorta itself serving to propel the slow-moving blood in 

 its course through the arterial system." Hence the demand for the 

 strength and thickness of the cod-sound, which I commend to the 

 biological attention of the readers of Knowledge when they next 

 partake of boiled cod-fish. Even though not " accustomed to the 

 use of the scapel," they will then be able to consider the probability 

 of this being merely devoted to holding air, while the " delicate 

 thin-walled tube, about one-twelfth of an inch diameter," which 

 " Old Fossil " found in the 8 or 9 lb. fish, propels the blood through- 

 out its body without any help from tho outer tough membrane of 

 the sound. W. M.4ttied Williams. 



ERRAxrM. — In letter on the Radiometer, p. 457, last line but one, 

 for Sodium read Iodine. 



Colliery " Spoil Baxks." — Tou are doubtless familiar with the 

 large heaps of refuse removed from coal-pits, technically known as 

 " spoil banks." These heaps are usually, though not always, on 

 fire, and when seen after dark present an appearance of wild and 

 magnificent grandeui-. I have often heard expressions of wonder 

 and admiration from persons who have seen these burning moun- 

 tains for the first time. It is my habit to look at these " mountains " 

 from a less romantic standpoint, as the sulphurous and other 

 noxious fumes arising from them are doubtless as injurious to 

 animal life as the appearance of the immediately surrounding dis- 

 trict proves them to be to vegetable life. 1 frequently hear the 

 assertion that these heaps fire " spontaneously." Will you kindly 

 give your opinion, through the columns of Knowledge, as to 

 whether this is likely to be ; and, if so, how it occurs ? How is the 

 chemical combination necessary to produce flame brought about ? — 

 One who wants Knowledge. 



