SEELYE: CIRCULATORY SYSTEM OF DESMOGNATHUS. 339 
Amblystoma opacum, a form with rudimentary lungs; Amblystoma 
punctatum, and one of our common frogs, for lunged forms. The 
results are shown as tabulated records below (p. 340). The appara¬ 
tus was allowed to remain in each case until the experiment came to a 
standstill, the liquid in the tube rising at first and then falling as the 
fluids inside and out became mixed through the integument, or until 
the experiment was interrupted for other reasons. 
The conclusion to be drawn from these experiments seems to be 
that the skins of the lunged forms are more easily and quickly per¬ 
meated by the liquid than those of the lungless forms. However, it 
is immediately seen that a larger number of such experiments is needed 
upon which to base any very sound conclusions. 
The problem in hand, moreover, was not how liquids could permeate 
the skin, but whether an exchange of gases 
could take place there. A more pertinent 
experiment was made by means of an 
apparatus shown in fig. B. Carbonic acid 
gas was used, with lime-water to test its 
presence. Four small vials (v.) were filled 
with lime-water, and over the tops were 
firmly tied pieces of integument ( i ., 1, 2, 
3, and 4), removed from four different 
amphibians, two lungless and two lunged 
forms. The animals used were Des- 
mognathus jusca, lungless; Spelerpes bilin- 
eatus, lungless; Amblystoma opacum, 
lungs rudimentary; and Diemyctylus 
viridescens, lungs fully developed. These 
four vials were then inserted in a cork disk 
(c.) to hold them upright, and this care¬ 
fully placed in a large-mouthed glass bot¬ 
tle. The large bottle was then filled w r ith 
carbonic acid gas and tightly closed with a 
rubber stopper. The apparatus thus set 
up was allowed to stand while the lime- 
water was carefully watched to see when it first became milky, a sign 
of the presence of co 2 , and when it again became clear, a sign of excess 
of co 2 . The results are tabulated below (p. 341):— 
From this experiment we may conclude that gases can permeate 
Fig. B.— c., cork disk; i., integu¬ 
ment: (1) of Amblystoma opa¬ 
cum, (2) Desmognathus Jusca, 
(3) Spelerpes bilineatus, (4) 
Diemyctylus viridescens; v., 
small vial filled with lime water. 
