1866.] 



Dr. Davy on the Bursa Fabricii. 



101 



soon as they are capable of fliglit, the bursa is comparatively large whilst 

 they are nestlings, does not increase conspicuously, if at all, with their 

 growth, but rather diminishes, and after a certain age disappears, and pro- 

 bably sooner than in the first mentioned. The buzzard and owl are ex- 

 amples, and probably all birds of the same family, all of the Corvinse, all 

 of the thrush kind, and all the smaller birds, with the exception perhaps of 

 the female martin. 



Of the uses of the organ, I venture to conjecture, founding my conjec- 

 tures on what I have observed, that they may be provisional and various ; 

 that in some birds, whilst nestlings, it may act the part of a urinary blad- 

 der, as witnessed in the instance of the young owl, and in some of the young 

 rooks, crows, and thrushes, thereby tending to prevent the fouling of the 

 nests ; that in others it may serve as a seminal reservoir at an early period, 

 and in both male and female in the instances mentioned, in which it has 

 been found most completely formed before the attainment of full size — 

 in the male before the vasa deferentia are fully developed, in the female 

 so long as the oviduct is still small and unexpanded ; and that generally, 

 as the organ is more or less amply supplied with mucous follicles, it may 

 serve, by the secretion it yields, to lubricate the cloaca with which it is 

 connected, and to aid in its functions. 



These conjectures, or inferences, if deserving of being so considered, might 

 be supported by what we know of the structure of the part and its position 

 in relation to the termination of the ureters, of the spermatic vessels, and 

 of the oviduct ; but I think it better to rest them on the facts observed — 

 the urinary matter detected in the organ in some instances, the spermatozoa 

 in others*, and the mucous fluid generally. 



But granting even that the bursa may be useful, and in the female as well 

 as in the male, in aid of fecundation, as Fabricius supposed, yet his extreme 

 view that that aid, in the stored-up spermatic fluid in the bursa of the hen 

 bird, might suffice for a year, as stated in the subjoined passagef , for which 

 and for other extracts I am indebted to the kindness of Professor Sharpey, 

 is both highly improbable, and is opposed by the fact of the decrease of the 

 bursa with the advancing age of the fowl, and the enlargement of the ovi- 



* As in no instance 1 have yet found unquestionable spermatozoa in the bursa of the 

 young hen, I cannot fairly infer that the bursa in the female is a receptaculum seminis ; 

 but as in two instances there were detected in it filaments which were very like these 

 bodies, and in one a single pretty distinct spermatozoon, and further, as the bursa seems 

 to diminish rapidly as the oviduct becomes developed and not till then, is it not probable 

 that for a short time it may perform the part assigned, as conjectured above? It need 

 hardly be remarked that the mucous secretion of the bursa adds to the difficulty of de- 

 monstrating the presence of spermatozoa. 



t " Semen autem Galli ad podicem immittitur, et in vesica reponitur et conservatur, 

 quousque pullus oonformetur ; immo veto per totum integrum anni tempus inibi servatur, 

 postea quam semel admisso Gallo, ova omnia per totum illud anni tempus foecunda red- 

 duntur, tanquam vesica unicum ob id foramen habente, ut in concluso loco semen Galli 

 diutius ut in proprio et congrno loco servetur."— 0/;/;. Omnia, Lugd. Bat. 1738, p. 21. 



