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Oiat upon one occafion, where we fed a fowl with madder 

 for n difTcrciit piirpofo, the cretaceous part of the cxcrenient 

 loll its ufiial whitcncfs, and became of tiie pale piiilc colour 

 which madder is well known to communicate to calcareous 



earths. 



Renal Capfules. 



Thcfe bodies hold the fam.- lituation in birds as in mam- 

 malia ; they alio ufiially poffcfs an irregularly triangular 

 figure. The propiirtion which they bear in fize to the 

 kidney, is pcrliaps kfs than generally occurs in q\iadrupals. 

 Ill tlie^o»/f, they are each about as large as a pea. The 

 colour of the renal capfules is in every inftance more or kfs 

 yellow. Several of the older anatomifls have defcrihed 

 a fingle renal capfule in fome fpecies of birds : the miilake 

 fccms to have arifen from their being occafionally fo clofely 

 applied to each other, that they appear as one body. 



The renal capfules of birds do not pofTcfs any cavity or 

 dilated part fcir venous blood, which renders it probable 

 that the enlargement of the capfular vein, which has at- 

 tracted fo much attention in the human fubjeft, is no way 

 concerned with the fundion of thefe bodies. 



Having difcuflld the llruflure and operations of tliofe 

 organs which are more immediately concerned in fupport- 

 ing the life of the individual, we fliall proceed to confider 

 thofe which are fubftrvient to the fecond order of func- 

 tions. 

 Organs employed in the Exercise op tiii; Gene- 

 rative Functions. 

 Mule parts of Generation. 



The tef.icles of birds are always two in number ; they are 

 fituate-d on the infide of the body, high up in the loins, 

 upon the fuperior edge of the kidnies ; from which pofi- 

 tion they never defcend at any period of life, as in mammalia. 

 Confequeiitly, birds are not provided with zfcrotiim, or any 

 external pouch for the accommodation of thofe glands. 

 The figuie of the tellicles are moll commonly oval ; oc- 

 cafionally they are of an elongated form, as in the cnffoivary. 

 See P/.;/f VII. in the y//M/o;HV of Birds ; fg. I. Somctime'S 

 the tefticlcs are nearly round, aa in tlie ciirnjfoiu, and other 

 inftances. 



The tefticles appear to receive a covering from the peri- 

 toneum ; but their proper tunic is remarkably ftrong, 

 denfe, and inclalHc. 



It will always be a matter of great difficulty, to exhibit 

 fatisfaflorily, the intimate (Iruftiire of the ttlles of birds, 

 ns a fuccef'fnl injeftion from the vas deferens is nearly im- 

 pofiible. The feminiferous tubes are fo tender, that they 

 do not fuftain the leall force without being ruptured ; and 

 at the period when the telles are fully developed, they are 

 loaded with their own fecretion, a circumllar.cc highly 

 unfavourable to the expofition of th.e ftruAure of thcfe 

 organs by tlie means of ii'jeftion. The blood-veffcls of tiie 

 tellicle are eafily traci.d ; fome of them pafs in the ufnal 

 manner direftly from the back part, through the glandular 

 fiibllancc, to the furface, where they unite with others 

 wiiich fpread in an ariiorcfcent foim, under the capfules of 

 the telles. The great mafs of thcfe glands is evidently 

 made up of tubes, which are convoluted in all directions, 

 and are feparated into bundles or packets, by verv thin 

 cellular membranes. Their conneftion with the fecrctory 

 extremities of the )' lermatic arteries, and thtir termination 

 in the excretory duci, are, however, involved in obfcurity, 

 for the reafons ahead ,■ given. 



The tellicles of birds dilfer very much in fi/e at difTertnt 

 feafons of the year. When tiiefe orgafis are not excrcifcd 

 in the ait of generation, they become reinarkalily diminidicd ; 

 but, during the period in which the female lays her eggs. 



B I R 



they acquire a bulk even beyond what might be expe£led, 

 from the fize of the bird to which they belong. This 

 fubjeft has been llrikin-ly illuftrated by Mr. Hunter, in a 

 fcrics of figures reprelcnting the variation of bulk which takes 

 place every fpring in the tefticlcs of the common fparrotu ; by 

 which it is fiitwn, that the tellicles of this bird are ordi- 

 narily about the fize of pin-heads, but, during the feafon 

 of propagation, ai quire ncariy the bulk of piilol balls. See 

 Plate Vli. in the Anatomy of Birds ; N"" l. exhibits the 

 telles as they exill in the month of January ; N° 2. as 

 they are in the middle of February ; N" 3. as they are 

 found in the beginning of March ; N' 4. their fize in the 

 latter end of March; and N°5. the bulk they alTume in 

 the middle of April. 



The I'as deferens, or excretory du£l, arifes ufualiy from 

 the pollcrior part of the tellicle, and probably always 

 fuffers a certain degree of convolution or coihng upon it- 

 felf, correfpouding to the cpldydlmls, which generally 

 differs more or lefs in colour from the body of the gland. 

 In the curnjpjiu and luflard, it has been obfcrved to be 

 black ; in the caffaiuary yellow ; and in the eirdea vlrgo, a 

 green colour. The academicians reprefent the cpidydimis 

 of the cajfoivary as being extended for fome way above 

 the tellicle, and confidcrably enlarged at the top. See 

 Plate VII. in the Anatomy of Birds, Fig. 1. aa the two 

 telles ; b b the epidydimis of each fide ; c c the vafa de- 

 fcrentia ; dd the ureters coming from the kidney to unite 

 with the vafa defereiitia ; / c the cxcreto: y dufts common 

 to both the kidnies and the tellicles. 



In the ojlrlch, the epidydimis turns up on the fide of the 

 tellicle ; and in the ardea I'lrgo, it is pendulous from it, 

 and only conneftcd by one end. The vas deferens alfo in 

 this bird, appears to arife from the body of the tcftis, in- 

 Head of the epidydimis ; and at its lower part, the du£t 

 unites with the ureters, in the fame way as is reprcfented in 

 the ca[f'jivary. In the cnjfoiuary, the epidydimis id fituated 

 below the tellicle, which it almoit equals in Ir/c. 



In moll birds the vafa deferentia proceed to their termi- 

 nation, without undergoing any remarkable degree of 

 convolution, or experiencing any dilatation analogous to the 

 veficuU femlnnles ; but in the cock, thcfe dufts are compofed 

 of convolutions or rcfleftions of a tube from fide to fids, 

 which are fo clofely applied to each other, that a longitu- 

 dinal feftion of the dudt prefents the appearance of a leries 

 of cells, which feeni to communicate with each other in the 

 middle. Thefe become larger and more numerous towards 

 the lower pari of the vas deferens, and are capable of con- 

 taining a confidcrable quantity of fcmen. It may be prefumed, 

 therefore, that the cck, and other falacious birds, are pro- 

 vided with 'thefe receptacles of femen to enable them to 

 meet the exigency of frequent copulat'on ; and it is alfo 

 to be obferved, that thofe birds which have the vafa defe- 

 rentia more finiply formed, do not perform the aft of 

 coition fo rapidly as the gallinaceous fowl. See Plate VII. 

 in the Anatomy of Birds. Fig. 2. exhibits the genital 

 organs of the common cock ; a a the tefticlcs of an oval Ihape ; 

 ^3 the epidydimis at the pollerior part of each; cc the 

 vafa deferentia, one of which is cut open to expofe the 

 loculated appearance it prefents internally. 



The/;rH;j-, in thofe birds where it has been obferved to 

 exi!l, is fixed upon the end of tl\e refitum, im.mediately 

 within the verge of the anus ; it is ufnally of a pyramidal 

 figure, and in its ordinary Hate is twilled hke a fcrew ; its 

 external tunic is derived from the intelline, and is formed into 

 a number of little rugae, or proceffcs, giving the edges of the 

 peni , in its contracted flate, a jagged or notched appear- 

 ance. The body of the penis ii compofed of a white llgj- 



mentoua 



fl 



