386 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOX,. 50 



The Sacci Abdominales 



Synonyms 



Bertelli: Sacchi posteriori. 



Campana: Receptacles inferieurs. 



Cants: Quartus magnus saccus seriferus. 



Colas: Sac intestinal. 



Fatio: Sacci renales et sacci abdominales propria? dicti. 



Gouillot: Reservoirs pneumatiques superieurs, suprarenales de l'abdo- 



men et abdominales inferieurs. 

 Huxley: Posterior air-sac. 

 Jacquemin: Poches pneumatiques sous-femorales, abdominales et 



sacrees. 

 Merrem: Die beiden Bauchsiicke. 

 Owen: Cellulse abdominales. 

 Sappey: Reservoirs abdominaux. 



The sacci abdominales are the largest" of all the air-sacs. They 

 also appear in the embryo at a much earlier stage than the others. 

 Bertelli says in regard to them (1900, p. 162)": "Gli abbozzi dei 

 sacchi posteriori sono i primi ad apparire. Alia settantaduesima 

 ora di prossimita degli estremi caudali tin leggerissimo rigonfiamento 

 che e l'abbozzo dei sacchi posteriori, incluso nei legamenti pulmonali- 

 epatici. Gli abbozzi dei sacchi posteriori et i sacchi posteriori sono 

 accolti nei legamenti pulmonali-epatici, nel polmone, nel diaphramma, 

 nelle pareti laterali dell' abdome dalle qnali sollevandosi invadoni la 

 cavita abdominale." 



The abdominal sacs enter the abdominal cavity dorsally and partly 

 enclose the viscera. Their walls are extremely elastic and almost 

 entirely free. They accordingly cling closely to the organs with 

 which they come in contact, and give off numerous diverticula, which 

 protrude into the spaces between the various viscera and between the 

 latter and the outer wall of the abdomen. The shape and distension 

 of the intestine are constantly changing ; reciprocal changes must 

 therefore constantly occur in the shape and distension of these air- 

 sacs. Sexual distinctions and the production of eggs are responsible 

 for reciprocal differences in the size and shape of these sacs in the 

 male and female bird. The variations in the distension of the ovi- 

 duct are particularly to be considered in this respect. In conse- 

 quence of all these circumstances the casts of these sacs vary very 

 much in different individuals when injected. In consequence of the 

 asymmetry of the viscera the two abdominal sacs are very asymmet- 

 ric, the right one (figs. 6, 11, and 12, SAD) being much larger than 

 the left (figs. 11 and 12, SAS), the development of the latter 

 being impeded by the stomach. The difference in relative size of the 



