Joseph Marshall Flint 133 
blood-vessels run. These lobules persist until adult life, although they 
may become compound by the rupture of the interlobular septa and the 
subsequent confluence of several adjacent lobules. ‘This process ordi- 
narily takes place at the base, leaving the periphery of the compound 
lobule separated by partial septa. 
18. The lymphatics appear at the root of the lung in an embryo 4-5 
em. in length. Accompanying the bronchi and pulmonary vessels, they 
gradually grow in for some distance until the smaller air passages are 
reached, when they leave these structures and grow towards the pleura 
in the interspaces between the smaller bronchi, in what represent the 
primitive interlobular spaces. In this way they aid in the differentiation 
of the connective-tissue lobules. The reason for this course is not entirely 
clear, but it may be due to the increasing density of the framework about 
the bronchi, which forces the later-appearing lymphatics into the inter- 
lobular spaces as a locus minoris resistentiz. Upon reaching the pleura, 
they turn and form a plexus in the subpleural connective tissue. Here 
and there, they may be seen penetrating the lobules, but cannot be fol- 
lowed for any distance in them. At 23 cm., the first evidence of the 
submucous plexus is seen in the stem bronchi. 
LITERATURE. 
Arspy.—Der Bronchialbaum der Saiigethiere und des Menschen. Leipzig, 1880. 
v. BaER.—Ueber Entwickelungsgeschichte der Thiere. Konigsberg, 1828. 
BicHat.—Anatomie descriptive. Paris, 1829. 
BLISNIANSKAJA.—Die Entwickelungsgeschichte der menschlichen Lungen. 
Diss. Zurich, 1904. 
BonNET.—Handbuch d. vergl. Histologie u. Physiologie der Hausséugethiere. 
Bd. 2, Berlin, 1892. 
BREMER.—American Journal of Anatomy. Vol. I, 1902. 
American Journal of Anatomy. Vol. III, 1904. 
CapiaT.—Jour. de l Anatomie et de la Physiologie. 1877. 
CoUNCILMAN.—Journal Boston Med. Soc. Vol. IV, 1901. 
Ewart.—The Bronchi and Pulmonary Blood-vessels. London, 1899. 
FISCHELIS.—Beitrage zur Kenntniss der Entwicklungsgeschichte der Lunge. 
Diss. Berlin, 1885. 
FiLint.—Johns Hopkins Hospital Reports. Vol. X, 1900. 
Journal of Medical Research. Vol. VII, 1902. 
— (1) American Journal of Anatomy. Vol. II, 1903. 
(2) Archiv. f. Anat. u. Ent. Anat. Abth. 1903. 
(1) Anatomischer Anzeiger. 1906. 
(2) Anatomischer Anzeiger. 1906. 
Fou.—Recueil zoologique suisse. T. 1, 1884. 
