AVES. 347 



Barn-Owl (Strix flammea) and Horn-Owl As might be expected from their relations 



( Otus aurita). The influence of these muscles to the pelvis, the kidneys in birds present as 



upon the voice must obviously be in proportion many varieties of outward configuration as 



as they shorten the bronchi and depress the there are differences in the part of the skeleton 



lower larynx, according to the different inser- to which they are moulded. In some aquatic 



tions above mentioned. birds, as the Grebe ( PodicepsJ and the Coot 



A further degree of complexity in the organ (Fulica), the kidneys are more or less 



of voice is presented by the Psittacida or Par- blended together at their lower extremities, as 



rot-tribe, which, according to Cuvier, have three in most fishes. In the rest of the class they are 



pairs of inferior laryngeal muscles. distinct from one another. 



- The Insessores, lastly, present five pairs of In the Tern they are each divided by fissures 



muscles appertaining to the lower larynx, and the into seven or eight square-shaped lobes. In 



organ of voice consequently attains its greatest the Eagle they each present four divisions ; but 



perfection in this order. in these cases there are not distinct ureters to 



The peculiar structure of the lower larynx, each lobe as in the subdivided kidneys ofmam- 



and the modifications of the trachea in relation malia. 



to its functions, will be treated of under the The principal lobes are in general three in 



article Organs of' Voice. number, the anterior or highest one being, in 



Urinary Organs. These consist in birds of some cases, the largest ; while in others, as 



the kidneys, ureters, and a urinary receptacle, the Pelecan, the contrary obtains, the lowest 



which is more or less developed in all birds. division being most developed in this bird. 



The kidney of the oviparous vertebrate ani- In the Emeu (Dromaius ater) the kidney 



mal is distinguished from that of the mammi- presents only two lobes ; the superior or anterior 



ferous by the homogeneity of its substance, one is the broadest and most prominent, being 



which is not divided into a cortical and medul- of a rounded figure, and constituting one-third 



lary part, and by the tubuli uriniferi extending of the whole ; the lower division is flattened, 



to the surface of the gland there to form by and gradually tapers to a point. In the speci- 



reiterated unions the ureter, and not terminating men we dissected we found the left kidney half 



in a cavity or pelvis in the interior of the kidney, an inch longer than the right, 



from which the ureter commences. Each kidney is invested by its proper capsule, 



The kidneys (x x, jig. 182) of birds manifest a thin membrane, which also extends into the 



all the essential characters of the oviparous type substance of the gland, between its divisions : a 



of structure. They are two in number, of an elon- delicate layer of peritoneum is reflected over 



gated form, commencing immediately below the their anterior surfaces. 



lungs, and extending along the sides of the spine The texture of the kidneys is much more frail 



as far as the termination of the rectum; in which than in mammalia, readily yielding under the 



course they are impacted in, and as it were pressure of the finger, to which they give a granu- 



moulded to the cavities and depressions of the lar sensation as their substance is torn asunder, 



pelvis. From this fixed condition it results that In colour they resemble the human spleen, 



they are generally symmetrical in position, not Besides being divided into lobes, the surface of 



placed one higher than the other, as in the mam- the kidneys may be observed to be composed of 



malia. The posterior surface of the kidney pre- innumerable small lobules, separated by conti- 



sents inequalities corresponding to the risings nuous gyrations like the convolutions of the 



and depressions of the pelvis; the anterior sur- cerebral substance. The ultimate divisions of 



face is smoothly convex or flattened ; but rising the lobules and their intimate structure can 



into a series of prominences which correspond, only be distinguished by observations on the 



not to the eminences, but to the cavities of the embryo, unless when the component follicles 



bones on which they rest : their inner or mesial are filled, as they occasionally are seen to be 



side is generally pretty regular and straight, but after death, with the white salts of the urinary 



the external edge is more or less notched. secretion. The tubuli uriniferi, as Miiller ob- 



From the nature of the integuments about to serves,* may then be seen under the microscope 



be described, and the small amount of cutane- originating from every part of the internal sub- 



ous transpiration in birds, the office of removing stance of the lobules, extending to the gyrations, 



from the system the superfluous watery part of uniting in the pinnatifid form, and coursing to 



the circulating fluids devolves almost exclu- the margins of the lobules, all the inflexions of 



sively upon the kidneys, and they are conse- which they follow. The pinnatifid ramification 



quently relatively larger than in the terrestrial of the uriniferous tubules is sometimes opposite, 



mammalia. sometimes alternate. Sometimes the branches 



The kidneys vary in size in different birds, are simple, sometimes dichotomously divided : 



being for example smaller in most of the but these ramuli appear scarcely smaller than 



Grallatores, as the Bustard and Heron, where the branches from which they spring, and never 



the pelvis is short, than in the Rasorial intercommunicate. They have been successfully 



Order, in which it is of great extent. Where injected with size and vermilion, without any 



they are short they are in general more promi- of this material escaping into the secerning 



nent, and this is so remarkable in some birds, vessels, which are much more minute. The 



as the Owls, that in them they resemble some- uriniferous ducts, when thus traced from the 

 what in their superficial position the kidneys of 



mammalia. * De Glandularum Structura, p. 92. 



