HUMAN LUNG 327 
vy. Ebner supports Miller’s statement, saying that the atrium 
is a regional division and needs special designation. Justesen, 
because of his examination of the ox lung, agrees with Muller. 
Later on Miller again published a refutation of the disagreement 
of several investigators. Schulze opposed Miller. 
In the irregular bifurcating branches of a tree no one characterizes 
the points, where a branch divides in two or more end branches, as 
special spots with proper name. In the same way it would also seem 
fitting to give no special designation to such points in the respiratory 
duct system of the lung. Miller’s atrium is merely the last end of an 
alveolar duct before it enters the terminal sacs. 
This contention is reasonable. Miller could prove that although 
an alveolar duct sometimes shows a sinuous expansion here and 
there before it breaks into the air-sacs, this does not take place 
constantly. Moreover, many lateral air-sacs are attached di- 
rectly to alveolar ducts without the interposition of a cavity. 
According to Sussdorf, when such dilatations chance to ap- 
pear, the atria are nothing more than the expansion in the 
dividing part of the air tubes. These expansions serve for the 
insertions of many branches. Keil could not find any atrium 
in the lung of sheep. While on the other hand he acknowledges 
the presence of atria in the dog lung. Miller in his later publi- 
cation of 1913 still maintains that there are atria in the cat lung. 
According to him, failure to recognize atria is due to three causes: 
that the study has been of but one section, that corrosion prepa- 
rations have been used, or that the specimen has been over- 
dilated. He says the mere removal of the lungs from the thorax 
and filling them with fixing fluids may so stretch and distort 
the atria that they may be mistaken for ductuli alveolares. 
The specimen used in the construction of my positive model 
was injected with fixing fluid after its removal from the thorax. 
They display no sign of over distention at all; moreover, I can- 
not see how the whole lung could lose its characteristics by such 
manipulation. 
Upon the examination of my model I notice that there are 
spaces where air-sacs are sent off, but upon closer study these 
‘so-called atria seem little more than short branches of alveolar 
