EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 249 



in alternate succession, and radiate in a stellate manner ; these are the 

 ultimate expansion of the tracheal tree. Each of these tubes terminates 

 in a small irregular, sinuous dilatation, elongated, and either single, 

 bifid or trifid, pierced in each of its compartments by one or more 

 orifices of the labyrinthine canals, and opening finally into one of these 

 which thus forms a continuation of the original canal. 



M. Bourgery proceeds to the description of the sanguiferous capillary 

 system. 



There are two kinds of pulmonary capillaries which appear to have a 

 corresponding difference in their functional destination. The one of these 

 is formed of an endless chain of annular vessels, and, speaking compa- 

 ratively, of considerable size. The other consists of a membranous net- 

 work of very minute capillaries, which .fill the areolse of the larger 

 vascular rings. 



1 . The annular vessels. These vessels are enclosed between the walls 

 of the air tubes. Their form and their anatomy are always the same. 

 A radical arteriole represents a stem, the divergent branches of which 

 form a cone or tree. Two principal ramifications arise from it and 

 penetrate the intercanalicular septa " en interceptant un premier canal 

 retreci dans 1'espace triangulaire qui le renferme," Beyond this they 

 surround the contiguous (aeriferous) canals by as many polyhedral or 

 circular rings formed by a single vessel. The same disposition is 

 repeated at short distances, all the canals being as it were thus sur- 

 rounded by annular vessels, interposed in their septa, of from -^ to \ of 

 their volume ( T ^ to -^ mill.) which anastomose with each other, at the 

 points where the circular turns touch back to back, or at the points of 

 intersection. At the other extremities the annular vessels by their junc- 

 tion again form branches, the inosculations of which constitute venules ; 

 so that on a section either between two branches arising from an arte- 

 rial trunk, or from two neighbouring arteries, or in the intermediate 

 space between the arteries and venules the surface is formed by a net- 

 work of these annular vessels, communicating with each other, or rather 

 continuous everywhere without interruption, and becoming less in 

 diameter from the branches towards the central point of junction. The 

 general aspect of this surface, penetrated in all directions by the canals, 

 which are bounded by the vascular septa, resembles a net. The same 

 disposition obtains at whatever inclination the sections may be made. 



2. Net-work of minute capillaries, This system of minute vessels, is 

 placed within the membranous wall itself of the aerian capillary canals, 

 both the bronchial ramified, and the labyrinthine branches. It is 

 seen then, at the surface separated from the atmospheric air, in the 

 normal state, merely by a very delicate expansion of membrane, and it 

 is situated on a plane more superficial, than the annular vessels which 

 run in the intercanalicular septa. 



In order to comprehend this system of the minute capillaries, it is 

 necessary to consider it under two aspects, first, in minute distinct 

 fractions, and, second, as a whole. 



1st, Considering it in parts. It occupies the areolse formed by the 

 annular vessels and their anastomosing branches, and forms in the 



