474 A. M. MILLER 



now known to obtain in the mammal. The two main purposes of 

 the present communication are therefore: 



1. The estabhshment of the presence of an anterior or jugu- 

 lar lymph sac in avian ontogeny. This will include a brief 

 account of the chief developmental stages, of the formation of a 

 definite sac by coalescence of numerous veno-lymphatic anlagen, 

 its temporary separation from the venous system, and its subse- 

 quent secondary and permanent union with that system. 



2. The demonstration of the identity of the genesis of the jugu- 

 lar lymph sac in bird and mammal by comparison of correspond- 

 ing stages in the chick and the cat. 



It should be stated here, moreover, that this communication 

 is limited to the specific case of the jugular lymph sacs, and that 

 it does not in any way refer to the development of the systemic 

 lymphatics. 



In 1900 Sala^ pubUshed his excellent account of the develop- 

 ment of the lymphatics in the chick, but he confined his attention 

 for the most part to the posterior lymph hearts and the thoracic 

 duct. He describes and figures certain vascular channels and 

 mesenchymal 'cords' in the region of the precaval veins, but 

 does not ascribe to these structures any role in the formation 

 of lymph sacs (hearts), looking upon them rather as factors in the 

 development of the thoracic duct. 



So far as the writer is aware, Mierzejewski^ is the only investi- 

 gator who has studied the development of the lymphatics in the 

 cervical region in birds, with the idea that these lymph vessels 

 are derivatives of veins and that they subsequently form struc- 

 tures analogous to the posterior lymph hearts (of Sala). As a 

 matter of fact, Mierzejewski goes only so far as to observe that 

 in the region where the subclavian, vertebral and jugular veins 

 unite, a plexus of lymph vessels (Lymphgefassplexus) arises by 

 enlargement and coalescence of branches of these veins and that 



' Sala, Luigi: Sviluppo dei cuori linfatici e dei dotti toracici nell' embrione 

 di polio. Ricerche fatte nel laboratoriode anatomia normale della R. Universita 

 di Roma, vol. 7, 1900. 



* Mierzejewski, L. : Bcitrag zur Entwicklung des Lymphgefasssystems der 

 Vogel (vorlaufige Mitteilung). Extrait du bulletin de racademie des sciences 

 de Cracovie, 1909. 



