URIXARY SYSTEM 69 



arise from the upper part of the nasal passages, and lie immediately 

 under the skin of the face. These appear analogous, although not 

 in the same situation, to the gular pouch of the male Bustard. 

 The larynx frequently has membranous pouches in connection 

 with it, into which air passes. These may be lateral and opening 

 just above the vocal cords, when they constitute the saccull laryngis, 

 found in a rudimentary state in Man, and attaining an enormous 

 development, so as to reach to the shoulders and axilla?, in some 

 of the Anthropoid Apes ; or they may be median, opening in 

 front either above or below the thyroid and cricoid cartilages, as in 

 the Howling and other Monkeys, and also in the Whalebone 

 Whales and Great Anteater. 



Urinary Organs. — The kidneys of mammals are more compact 

 and definite in form than in other vertebrates, being usually more 

 or less oval, with an indent on the side turned towards the middle 

 line, from and into which the vessels and ducts pass. They are 

 distinctly divided into a cortical secretory portion, composed 

 mainly of convoluted tubes, and containing the so-called Malpighian 

 bodies ; and a medullary excreting portion, formed of straight tubes 

 converging towards a papilla, embraced by the commencement of 

 the ureter or duct of the organ. The kidneys of some mammals, 

 as most Monkeys, Carnivores, Rodents, etc., are simple, with a 

 single papilla into which all the renal tubuli enter. In others, as 

 Man, there are many pyramids of the medullary portion, each with 

 its papilla, opening into a division (calyx) of the upper end of the 

 ureter. Such kidneys, either in the embryonic condition only, or 

 throughout life, are lobulated on the surface. In some cases, as in 

 Bears, Seals, and especially the Cetacea, the lobulation is carried 

 further, the whole organ being composed of a mass of renules, 

 loosely united by connective tissue, and with separate ducts, which 

 soon join to form the common ureter. 



Bladder. — In all mammals except the Monotremes the ureters 

 terminate by slit-like valvular openings in the urinary bladder. 

 This receptacle when filled discharges its contents through the 

 single median urethra, which in the male is almost invariably 

 included in the penis, and in the females of some species of Rodents, 

 Insectivores, and Lemurs has a similar relation to the clitoris. In 

 the Monotremes, though the bladder is present, the ureters do not 

 enter into it, but join the urino-genital canal some distance below 

 it, with the orifice of the genital duct intervening. 



VI. NERVOUS SVSTEM AND ORGANS OF SENSE. 



Brain. — The brain of mammals shows a higher condition of 

 organisation than that of other vertebrates. The cerebral hemi- 



