268 HERBERT G. WILLSON 
of the nineteenth century, when Soemmering, Rossignol, Reis- 
seisen, and others published the results of their researches, and 
Henle, by his discoveries in general histology, laid the founda- 
tion for many special investigations. Controversy now arose 
in regard to such questions as the exact shape of the terminal 
bronchioles, their method of branching, and as to whether or 
not there were direct communications between alveoli. 
Rossignol, writing in 1847, refers to the most distal divisions 
of the bronchial tree as ‘infundibula,’ and these he describes as 
being thickly beset with alveoli. He notes that the alveoli of 
the infundibulum are of an unusually: great depth, and that while 
the alveoli are scattered and few in the proximal part of the 
respiratory bronchiole, they are soon arranged close together, 
covering the whole surface of the last bronchial divisions. As 
to the method of branching, he concludes that there are both 
dichotomous and trichotomous divisions. In his investigations 
Rossignol inflated and dried the lung, after having injected the 
blood vessels. 
In 1860 Waters described monopodial, dichotomous and trichot- 
omous branching. His conclusions were based on the study of 
single sections. In man he found no alveoli in the terminal 
bronchiole, but only in the infundibulum. He states that at a 
certain place the terminal bronchiole widens into a cavity into 
which open six, eight, or ten canals, beset with alveoli. These 
canals he terms air-sacs, these being again identical with Rossig- 
nol’s infundibula. 
I. E. Schulze in 1871 used the term ‘Alveolengang’ to denote 
all the parts of the tubular system on which there are alveoli, 
excepting, however, the terminal sacs, for which he employed 
the term infundibula. 
In 1892 W. 8. Miller announced the discovery of a new ele- 
ment in the series of pulmonary air-spaces, terming it the ‘atrium’ 
and locating it between the air-sacs (infundibula) and the ter- 
minal bronchiole (alveolengang). This space seems to be identi- 
cal with the enlargement of the terminal bronchiole described 
by Waters as giving origin to the air-saes, but Miller describes 
it as something more than a mere enlargement, having a more 
