20 The Development of the Lungs 
tracheal musculature into the muscle of Reisseissen in the successive 
branches of the bronchial tree. He finds the entire stem bronchus until it 
is past the divisions of the upper and middle lobe and projects well into 
the lower lobe has a musculature like the trachea. On the other hand, the 
bronchus of the upper, middle, and then lower part of the stem has the 
muscle of Reisseissen. These findings, Guyesse believes, give evidence 
that the production of the main bronchi is by monopodial growth. 
Miller, oo, while working chiefly on the anatomy of the lobule, agrees, 
apparently, with Aeby’s division of the eparterial and hyparterial region 
of the human lung, and, furthermore, he also speaks of monopodial 
division of the tree. 
According to Justesen, 00, who studied the branching of the bronchial 
tree chiefly in cow embryos of well-advanced stages and in post-natal life, 
the division of the bronchi from first to last takes place by undoubted 
dichotomy after which the asymmetry is produced by unequal growth of 
the stem. This author approves of His’ attitude towards Aeby’s theory 
of monopodial development in general, but criticises his belief in the 
production of the first branches of the tree by monopody without having _ 
the material to follow their successive development. It seems rather 
strange, therefore, that Justesen, who was himself without these stages, 
should attempt to prove from His’ illustrations in which these branches 
were already formed, that they originated by sympodial dichotomy 
especially after remarking so wisely, “ Es ist kein Versuch, die Frage 
durch unberichtige Analogie folgerungen zu lésen. Ich will nur behaup- 
ten, dass die Frage nicht gelést ist, weitere Untersuchungen dagagen 
nétig sind.” Justesen does not believe in the production of bronchi by 
lateral outgrowths of the mother stem. He believes, therefore, Stieda’s 
observation was faulty and states that no other investigator has since 
repeated this observation. He is ignorant, apparently, of the work of 
Robinson, d’Hardiviller, and Nicholas and Dimitrova. 
Justesen does not accept Aeby’s distinction between the eparterial and 
hyparterial regions of the bronchial tree and looks upon the accessory 
bronchi of Aeby as independent structures. Their irregularity he 
ascribes to the presence of the heart and vertebral column. 
Merkel, 02, agrees with His, that the first divisions of the stem 
bronchi are produced by monopodial growth and that the later divisions 
arise by dichotomy. With Narath, he abandons Aeby’s distinction be- 
tween the eparterial and hyparterial region as resulting from the in- 
fluence of the pulmonary artery on the architecture of the tree, and 
looks upon the right apical bronchus, the so-called eparterial, as a 
derivation cf the first ventral and homologous with the apical branch of 
