XXll 
INTRODUCTION. 
called, from its discoverer, the bursa Fabricii. The kidnies lie in the 
excavation of the back-bone, and are flat and of a purplish colour, and in 
general form a double row of distinct, glandular bodies ; from them runs 
a whitish-coloured duct, which terminates in the common cloaca, making 
an aperture distinct from that in the poenis. We shall in our cursory 
survey, slightly notice the principal differences in the skeletons of birds, 
as compared with those of the Mammalia; but we cannot enter on this 
subject without making a few short observations on their brain. Their 
cranium is more cavernous than that of man, and the brain itself differs 
from ours in the smoothness of its surface, the few, if any, circumvolu- 
tions on its exterior, in the form of the optic thalami, and by the want, as 
is generally supposed, of many parts which are found in the human brain, 
such as the corpus callosum, fornix, pons varolii, testes, &c. which, if they 
exist in birds, have not as yet been discovered ; and more peculiarly in the 
The bursa Fabricii is, in most birds, of an oval form ; but in some of the species, it is 
nearly globular. It was for a long time supposed that birds had no lacteal vessels, but that they 
possess them has been put beyond the reach of doubt. 
Coitus avibus trlbus modis, faemina considente } ut in gall inis, accipitribus vel passeribus ; 
aut stante, ut in gruibus ; aut in acre, ut in apis hirundinibus. Testiculi masculini, intra corpus 
dorso, infra jecur affixi sunt. Verno tempore turgent, et hunt quinquies majores, quam 
hyberno. Hi non sunt dissimili forma, sed alter plurimum alter! magnitudiqe prsestat. Avibus 
terrestribus, duae perexiguae partes generationis sunt intra corpus : sed aquaticis una sola per- 
grandis est. Per compressionem, aves terrestres potius quam ingressum, per ingressum aquaticae, 
coeunt. Harvoeus inquit..” In avibus et serpentibus, quibus fungosi sunt pulmones, parva 
cernitur urinae copia, quod parum admodum et pitissando bibant, et eorum nonnullae, nimirum 
aquilae, nihil omnino ; quare vesica urinaria iis non est opus, sed lotium in communem cloacam 
alvi quoque foecibus dicatam destillant, iisdeinque commistum simul egeritur. DifFert hoc lotium 
in avibus atque in aliis animalibus ; nam cum urinae partes duae sunt, serosior una et liquida, 
crassior autem altera, quae in sanis hypostasis nominator, et in urina jam refrigerata subsidit. Aves 
(contra quam vivipara animalia) majorem hujus copiam obtinent, eaque ab altera colore albo seu 
argenteo distinguitur ; et non modo in cloaca reperitur (ubi abundat) alvique fceces circumlinit ; 
sed etiam in toto ureterum ductu, qui a renum tunicis hac ipsa albedine discernuntur. 
