99 



XVI. — On a peculiar arrangement of Blood-vessels in the Air-blad- 

 der of Fishes, with some remarks on the evidence which they 

 afford of the true function of that organ. By John Quekett, 

 Assistant Conservator of the Museum of the Royal College of 

 Surgeons of England. 



Read July 20, 1842. 



The singular and beautiful manner in which the minute blood-ves- 

 sels of the various tissues and organs of the animal body are arranged, 

 have formed, since the time of Malpighi, Ruysch, Lieberkuhn, and 

 the older anatomists, some of the most interesting and important sub- 

 jects of microscopical investigation. So constant is the distribution 

 of the capillary vessels in the same tissue or organ throughout the 

 animal kingdom, that not only can they be classified, but even the 

 particular function which a part performs can, by the initiated, be at 

 once pronounced from an inspection of its blood-vessels. The re- 

 searches of Mr. Dalrymple, " On the Vascular Arrangement of the 

 Capillary Vessels of the Allantoid and Vitelline Membranes of the 

 incubated Egg," which were communicated to the Society at one of 

 its earliest meetings, affords an excellent example of the importance 

 of this subject, since from the arrangement of the capillaries alone in 

 the injected allantoid membrane, he has by the assistance of the mi- 

 croscope been able to point out the true respiratory function of this 

 membrane, by showing that the vascular net-work is precisely similar 

 to that found in the lungs of other vertebrate animals, and by this 

 means to settle satisfactorily a long-disputed question. 



Among the most common, and now most easily recognized classes 

 of vessels, are those which characterise the cutaneous, muscular and 

 respiratory systems. Most anatomists are familiar with other classes, 

 but to no known class that I am aware of, can some of those found in 

 the air-bladders of fishes be at present referred. Anatomists, with 

 very few exceptions, appear to have passed over this subject in si- 

 lence. All authors agree in mentioning the fact of the great vascu- 

 larity of the interior of the bladder ; but the minute vascular arrange- 

 ment which could not well be studied without the aid of injection, 

 has been overlooked : the great difficulty of injecting fish, on account 

 of the weakness of their vessels, is perhaps the principal reason of this 

 part of their anatomy being undescribed. The difficulty of the injec- 

 tion must have been well known to Fischer, a German anatomist, for 



