. The American journal of anatomy. on is composed of young connective tissuewith well-marked fibrils. As the mesoderm differentiates, therefore, itl)ecomes firmer and is less easily influenced by the growth of the youngbronchi. Fig. 20 is an outline drawing of the lateral and diaphragmatic aspectsof the lungs of an embryo 19 cm. long. At this time, all of the importantadult topographical features of tlie lungs are present. . shows well howthe right Lobus superior has grown down and back into the dorsal area,moulding itself even more than in an emljryo mm. long (Fig. 19)to that portion
. The American journal of anatomy. on is composed of young connective tissuewith well-marked fibrils. As the mesoderm differentiates, therefore, itl)ecomes firmer and is less easily influenced by the growth of the youngbronchi. Fig. 20 is an outline drawing of the lateral and diaphragmatic aspectsof the lungs of an embryo 19 cm. long. At this time, all of the importantadult topographical features of tlie lungs are present. . shows well howthe right Lobus superior has grown down and back into the dorsal area,moulding itself even more than in an emljryo mm. long (Fig. 19)to that portion of the thoracic cavity and extending now up over the6 82 The Development of the Lungs base of the heart beyond the midline making the sum of lung tissue inL. 1 and L. 2 considerably greater than that in L. 2 on the opposite to this growth, the Lobus medius is pressed ventralwards, itsdorsal segment lying in the angle between the Lobus superior and theLobus inferior. It may be interesting to note, that the portion of the. Text Fig. Fig. 20. Outline drawings of the lungs of a pig 19 cm. Right side. B. Left side. C. Diaphragmatic surface. At this stage, thesurface of the lungs is smooth. The topography of the bronchi beneath,taken from corrosion specimens of the same age, is indicated by dotted linesand letters. lobe which lies in this angle, is supplied by the large dorsoinferiorbronchus. It is, therefore, ontogenetically equivalent (vide PI. II,Figs. 15, 16) to the apical segment of the Lobus superior on the otherside. Xothing could indicate clearer the adaptation of the growing Joseph Marshall Flint 83 bronchi to their environment, or the possible influence of environmentupon the branches of the tree. The tips of the Lobns medius havegrown around the heart until they have almost met in the midline. Onthe undersurface, the unpaired Lobus infracardiacus (Fig. 20, V. 2)is clearly seen particularly in its relationship to the Vena cava inferior. With the i
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectanatomy, bookyear1901
