378 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 50 



vertebra into the spinal Canal, where it unites with the corresponding 

 tubule from the opposite side, both together forming a duct similar 

 to the canalis supramedullaris (figs. 1, 2, 12, MEP). This duct 

 extends backward but does not reach the last thoracic vertebra. It 

 is very variable, and sends fine branches into the vertebrae and the 

 ribs. According to Baer (1896, p. 434), small diverticula, similar 

 to the canales intertransversarii in the neck, arise from this duct and 

 surround the costo-vertebral articulations. I have not been able to 

 make out anything of this kind in the pigeon. The lungs of the 

 pigeon insinuate themselves so completely between the costo-verte- 

 bral articulations that, if such diverticula were present, they would 

 penetrate into the lungs. It has sometimes seemed to me that the 

 ribs were pneumatized directly from the lungs. As a rule, however, 

 the ribs, as is always the case with the vertebrae, are supplied from 

 the medullary canal by means of fine tubules. 



The Sacci Cervicales in Other Birds 



Almost all birds possess, like the pigeon, sacci cervicales, but in 

 other species they are usually differently shaped. In the stork, the 

 flamingo, and the crested screamer (Chaitna) they are divided by 

 numerous partitions into a corresponding number of small spaces. 

 In the albatross, Ulrich has found (1904, p. 30) a tripartite division 

 of these sacs into a median unpaired one and two lateral symmetrical 

 ones. In the cockatoo, Bignon discovered (1887, p. 36) lachrymal, 

 ethmoidal, and supramaxillary extensions of the cervical air-sac 

 system. In this bird also occipital, frontal, parietal, quadratal, and 

 mandibular air cavities are found. These, however, are not true 

 (pneumonial) air-sacs, but diverticula of the nasal chambers. A 

 diverticulum of the cervical system which is entirely wanting in the 

 pigeon is described by Baer (1896, p. 434) as follows: "Bei manchen 

 Raubvogeln, beim Bussard, fand ich endlich eine dritte Fortsetzung 

 der Cervikalsacke. Dieselbe zieht sich als ziemlich weite, in regel- 

 massigen Abstanden perlschnurartig eingeschnurte Rohre, nur von 

 Hautmnskeln des Halses bedeckt, zu beiden Seiten der Spinalfort- 

 satze nach oben bis zum Hinterhauptsbein, wo sie blind endigt." 



The Saccus Interclavicularis 



Synonyms 



Bertelli: Sacche interclaviculare. 

 Campana: Receptacle superieur anterieur. 

 Corns: Erster Luftsack. 

 Colas: Sac cardiaque. 

 Girardi: Grosse Brustzelle. 



