Production of Isinglass from Indian Fishes 54<7 



without appearance of illness, till the 28th of June, when it was at- 

 tacked by convulsions, and died. 



A paper was read " On the polarizing property of living animals 

 and animal substances upon the rays of transmitted light," by Mr. 

 J. F. Goddard*. 



In this communication Mr. Goddard first alluded to the double 

 refracting (polarizing property) exhibited by the lenses of the eyes 

 of fishes and several other animal substances, an account of which 

 was published in 1816 by Sir D. Brewster. 



On repeating these experiments, Mr. Goddard, after observing 

 that the scarf skin of the human subject, sections of human teeth, 

 the finger nails, bones of fishes, and other substances, possessed the 

 same property, was led to examine some living objects, when he 

 discovered that among others, the larvae and pupae of a gnat (Co- 

 rethra j)lmnicornis) possessed this property in an eminent degree. 

 The extraordinary transparency of this little insect is such, that the 

 whole of its internal structure is beautifully displayed, and when 

 viewed by polarized light, presents the most splendid appearance ; 

 the peculiar interlacing of the muscles of the body, dividing it into 

 regular parts, present (as the insect changes its position with regard 

 to the plane of polarization) the most varied hues and brilliant co- 

 lours. Mr. Goddard stated that the same phsenomena may also be 

 seen, if possible, in a more splendid manner, in the spawn of many 

 large fislies, which, in their early state are sometimes equally trans- 

 parent, particularly those species which inhabit the sea. 



The polarizing property of various substances was beautifully ex- 

 hibited by Mr. Goddard, by means of his " Polariscope." 



July 23. — The following paper, on the production of Isinglass 

 from Indian Fishes, by Dr. Cantor, Corresponding Member, was 

 read : 



" In the December Number, 1838, of Parbury's Oriental Herald 

 appears a letter ' On the Suleah Fish of Bengal, and the Isinglass it 

 affords' : the description of this fish I shall quote in the words of 

 the anonymous writer. ' The Suleah Fish,' he observes, * when at 

 its full size, runs about four feet in length, and is squaliform, resem- 

 bling the Shark species in appearance, but exhibiting a more delicate 

 structure than the latter. The meat of this fish is exceedingly 

 coarse, and is converted by the natives, when salted and spiced, into 

 " burtah," a piquant relish, well known at the breakfast-tables of 

 Bengal. The bladder of the Suleah may be considered the most 

 valuable part of it, which, when exposed to the sun and suffered to 

 dry, becomes purely pellucid, and so hard that it will repel the edge 

 of a sharp knife when applied to it. These bladders vary from half 

 a pound to three quarters of a pound avoirdupois in weight, when 

 perfectly dry. . . . The Suleah Fish abounds in Channel Creek, off 

 Saugor, and in the ostia or mouths of all the rivers which intersect 

 the Sunderbuns, and are exceedingly plentiful at certain seasons.' 



" Conceiving the great importance of the discovery of isinglass 

 being a product of India, I was naturally anxious to examine the 

 * See the present volume, p. 162. 

 2N2 



