GILLOTT, JOSEPH, 1800-72; an English manufacturer known the world over for his steel pens. His first effort in this direction was in a garret, and the result, sold to small shop-keepers in Birmingham. They were stiff and awkward "barrel pens." From time to time he made important improvements, until his pens almost entirely superseded the goose-quill. Of late years the work of his own manufactory has reached the enormous number of 150,000,000 per annum. He accumulated vast wealth, and left at his country seat a remarkably valuable gallery of paintings and other works of art. GILLS, or BRANCHLE, are the respiratory organs of those animals which obtain the oxygen necessary for their well-being not directly from the atmosphere, but from the air held in solution in the water in which they live. In animals modified for pheric respiration, the air enters the system to meet the blood, a peculiar set of ments, more or less complicated, being appointed for its constant renewal. In aquatic animals, on the other hand ing aquatic mammals), a different plan is required, in consequence of the small quantity of air contained in the water; and hence the Orat• ing surface is extended outwardly, so as to yield a larger space than could be obtained in the interior. The blood is being perpetually driven along this surface, which is so constructed as to admit freely of the passage of air; and by the natural movements of the body, or by others of a special nature, a fresh supply of aUrated water is constantly afforded. The chief forms of respiratory apparatus in classes of animals are shoWn in the accompanying diagram, borrowed from Dr. Carpenter's Comparative Physiology. "Let AB represent the general exterior sur face of the body; then at a is shown the character of a simple outward extension of it forming a foliaceous gill, such as is seen in the lower crustacea; and in like manner, b may represent a simple internal prolongation or reflection, such as that which forms the pulmonary sac of the air-breathing gasteropods. A higher form of branchial apparatus is shown at c, the respiratory surface being extended by the subdivision of the gill into minute folds or filaments, as we see in fishes; and a more elevated form of the pulmo nary apparatus is seen at d, the membranous surface being extended • by subdivision of the internal cavity, as in birds and mammals. Lastly, at e is shown a plan of one of the " pulmonary branchim" of the arachnida, which forms a kind of transition between the two sets of organs—the extent of surface being given by gill-like plications of the mem brane lining the interior of a pulmonie cavity." We shall notice a few of the different forms of gills that occur in various classes. It is in the annelida that we find the fint distinct organs of this kind. Their blood is transmitted to a series of gill-tufts, which are composed of delicate membrane pro longed from the extreme surface, and which may assume the form of branching trees or of delicate brushes made up of a bundle of separate filaments. These tufts are sup
plied freely with blood-vessels; and fresh portions of blood and of water are stantly brought into contact by the natural movements both of the animal and the surrounding medium, and by the action of the cilia covering the respiratory organs. The tufts are sometimes attached at intervals along the whole length of the body, as in arenicola, in which there are 13 pair (see ANNEL1DA); while in other cases they occur about the head only. In the latter case, they are extremely beautiful, having the appear ance of a flower endowed with the most brilliant tints. Two animals common in the aquarium, the serpula and the terebdla, owe their resplendent beauty to these tufts (see figure under SERPULA). In all of the crustacea, excepting some of the lowest forms, whose general surface is soft, gills are present. The branekiopoda, belonging to the sessile-eyed crustacca, or edriophthalrna, are so called because their fins or feet present the form of simple plates or flattened vesicles, which float in the surrounding fluid, and expose the blood to the oxygen which the water contains. The branchim may be appended to the thoracic limbs in the form of membranous plates (as in antphipoda), or to the abdominal limbs as subdivided lamellae (as in isopoda), or the branchial plates may expand into vesicles attached to the thoracic feet (as in lcemodipoda). Amongst the crustacea with eye-stalks, or podophthalma, the respiratory plates, in the order stomapoda, are external, and are appendages' of distinct locomotive organs, each plate being divided. into a series of small filaments or tubes, so as to resemble a broad feather. Their posi tion is abdominal, as is seen in squilla. Here the gills have begun to assume more of the character they present in fishes, the laminated or leaf-like form being replaced by one in which the surface is greatly extended by minute subdivisions into delicate fila ments. In the order decapoda, including the crab and lobster, the respiratory organs. are of a more special character, and are lodged in branchial chambers protected by the carapace. A special apparatus is here found for the purpose of securing a constant cur rent of water over the aerating surface. The gills in these animals are in the form of long, slender, quadrangular pyramids, and consist either of numerous thin plates or minute cylinders arranged perpendicular to the axis of the pyramid. There are 9 such branchial pyramids on each side in the crabs, while in the lobster there are 22. For further details on the respiratory organs of the crustacea, the reader is referred to prof_ Owen's Lectures on the Comparative Anatomy and Physiology of the Invertebrate Animals, 2d edit., 1855, pp. 820-322.