AUTHOR’S ABSTRACT OF THIS PAPER ISSUED 
BY THE BIBLIOGRAPHIC SERVICE, MARCH 27 
THE TERMINALS OF THE HUMAN BRONCHIOLE 
HERBERT G. WILLSON 
University of Toronto 
NINE FIGURES 
In the hope of throwing some light on certain questions about 
which there has been controversy, the construction of a wax 
model of a respiratory bronchiole was begun at the University 
of Toronto in October, 1919. The work was carried out in 
collaboration with Prof. J. Playfair MeMurrich, by whom the 
problem had been suggested and to whom the writer is very 
greatly indebted for advice and assistance. 
The extreme complexity of the terminal branches of the bron- 
chial tree is not generally appreciated. The maze of channels 
which occur even in a minute piece of lung tissue cannot be 
visualized accurately from a mere comparison of serial sections. 
The larger passages of the lung may be injected with wax or 
metal and a cast obtained by corroding away the lung tissue, 
but one cannot be certain of obtaining in this way a complete 
cast of the smaller tubes. The method of wax reconstruction 
of serial sections is the only plan by which one may hope to get 
clear ideas regarding the finer tubes, and even this method is 
especially difficult to apply to the bronchioles. So complicated 
are the branchings and so carefully has nature economized space 
in the lung, that if all the air passages in a piece of lung tissue 
are reconstructed in wax on a magnified scale, the result is prac- 
tically a solid, and the model has to be dissected in order to show 
the relationships of tubes and air-cells. 
Malpighi in 1661 demonstrated the vesicular nature of lung 
tissue and showed how the trachea terminates in bronchial fila- 
ments, but after his time there was no important contribution 
to the knowledge of the histology of the lung until the early part 
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