AIR SPACES IN LUNG OF CaT 461 
occur.’ Later on, under the heading ‘‘Even dichotomy unsuit- 
able for the lung,’”’ he says in regard to dichotomy that 
It constitutes, so to say, the alpha and omega of bronchial division. 
But absolute evenness of dichtomy is not to be looked for. Due re- 
gard being paid to the shape of the thorax, unevenness is more likely 
than regularity. The products of a dichotomy which had beerf carried 
through with mathematical precision would have fitted ill within the 
pleural boundaries. Nay, even the more elastic principle of ‘mono- 
podial branching’ requires, in its working, to be allowed some latitude. 
All so-called principles, or laws, are overruled by a higher law, the law 
of adaptation. 
When this statement is taken into consideration it seems to 
me that we can no longer consider Ewart as believing in an even 
dichotomy, but must place him with those who believe in an 
uneven dichotomy. Moreover, when we reread the last state- 
ment in the above quotation, there does not seem any appreci- 
able difference between it and the statement of Flint when he 
says: ‘‘The bronchi, apparently, show great adaptability both 
in the power and direction of their growth.” In fact Ewart ap- 
parently was the first to advance this theorem. 
In his summary Ewart says: 
(1) All bronchi are dichotomous; (2) that in any bronchial pair, the 
greater size of one bronchus is correlated with the greater mass of lung 
tissue which it must supply with air. Thus unevenness of size is not 
necessarily a negative evidence against dichotomy; and dichotomy does 
exist, at any rate in the limited sense that never more than two branches 
arise from any one division. 
Huntington, through essentially different methods, arrived at 
the same conclusion as Ewart; that the type of division is dichot- 
omous. 
Miiller studied the mode of division in the adult whale and 
came to the conclusion that ‘“‘each main bronchus sends off 
branches in a strictly monopodial manner.” 
Schaffner bases his opinion on his study of the cardiac bron- 
chus of man and agrees emphatically with Aeby. He says: 
The cardiac bronchus divides into two branches, a ventral, smaller 
and a dorsal, larger. The dorsal . . . . divides aude 
again into two branches, an inner and an outer . . . . These 
