AVES. 



355 



everted, and the semen brought into contact with 

 the similarly everted orifice of the oviduct in the 

 female, along which the fecundating fluid is 

 impelled by the vibrations oi' the cilia or the 

 mucous surface through all the windings of 

 that tube to its ultimate destination. 



In the Natalores which copulate in water 

 there is an obvious necessity for a more effici- 

 ent coitus than a simple contact of everted 

 cloacse, and consequently in these birds, as the 

 Swan, Gander, Drake, &c. a long, single penis 

 is developed. 



Fig. 184. 



Penis of a Drake. 



This body arises from the front part of the 

 outer compartment of the cloaca (a, a, Jig. 184) 

 immediately below the urethro-sexual cavity; 



it is in the unexcited state coiled up like a 

 screw from the elasticity of the internal liga- 

 mentous structure. The external coat is a pro- 

 duction of the membrane lining the outer 

 cavity, and gives ofi a number oi' small pointed 

 processes, which in the Gander are arranged in 

 transverse rows on either side the urethral 

 groove, and near the extremity oi' the penis are 

 inclined backwards. The body (b b, Jig. 184, 

 where it has been cut open) is composed of a 

 white elastic ligamentous substance, and a 

 vascular pulp, but without any of the cellular 

 structure which characterizes a corpus caver- 

 nosum. A groove (dd), commencing widely 

 at the base is continued along the side of the 

 ligamentous substance, and follows all the 

 spiral turns of the penis to its extremity. 

 The vasa deferentia terminate in papilloe at 

 the base of this groove, along which the semen 

 is transmitted to the vagina of the female.* 



The penis of the Ostrich is also single, and 

 the urethra is represented by a dorsal groove ; 

 it is disposed in a slight spiral bend when in a 

 retracted state. It arises by two strong liga- 

 mentous crura from the cartilage uniting the 

 bones of the pubis, and descends into the 

 external or preputial compartment of the 

 cloaca. There are four muscles to the penis 

 of the Ostrich : two arise from the inside of the 

 os sacrum, and descending along the preputial 

 cavity, are inserted into the base of the penis : 

 two other muscles pass from the internal part 

 of the iliac bones, to be attached to the sides 

 of the penis. 



The Guan (Penelope cristata) presents a 

 singular exception to the other Rasorial Birds 

 in having a single linguiform pointed penis 

 developed, the sides of which are provided 

 with retroverted papilla?, as in the Anserine 

 Birds. In the Gallinule, which seeks its food 

 in water, there is no penis ; it, therefore, most 

 probably copulates on land. 



The tumid margin of the preputial cavity 

 of the penis is well provided with large mu- 

 cous follicles which secrete a sebaceous lubri- 

 cating substance ; of these there are twelve in 

 the Gander, arranged six on each side. These 

 may be regarded as analogous to the glandules 

 odoriferte ; but there is no vestige either of 

 prostatic or other urethral glands. 



Female organs of generation. An ovarium 

 or productive organ, (a, b, c, d, Jig. 185,) with 

 an oviduct or efferent tube (e, f, g, k, I,) are 

 present in all birds, and a clitoris or organ of 



* We cannot account for the error into which 

 Sir Everard Home has fallen, in describing the 

 urethra of the drake as a complete canal, and the 

 penis as being enclosed within a prepuce. (Phil. 

 Trans. 1802, pp. 361,363.) Repeated dissections 

 of different species of Anas, Cuv. have satisfied 

 us of the accuracy of Mr. Hunter's statement, 

 that " birds have no urethra, some having merely 

 a groove, as the Drake and Gander, and many 

 being even without a groove, as the common Fowl." 

 Animal (Economy, p. 40. The letter c, in Sir 

 Everard Home's figure, (fig. 184,) points to the 

 orifices of mucous glands or cut vessels, and not to 

 the papillae, on which the vasa deferentia termi- 

 nate. 



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