462 ANDREWS: PROTOPLASMIC STREAMING IN Mucor 
another efficient method I have used.* In some of my experi- 
ments, not shown in FIG. 1, I made connections between glass 
tubes in the following way, which were absolutely proof against 
leakage. 
The method may be illustrated by the accompanying diagram, 
: F FIG. 2. Tubes of somewhat different but con- 
venient sizes were used. The inner surface of 
ee A from C to D and the outer surface of B over 
eee the same distance were covered with paraffin 
and then these parts submerged in hydrofluoric 
acid. This etched the unparaffined surfaces of 
the tubes and allowed a more perfect and firmer 
© cisaud u grip of the sealing wax used in making the con- 
nection. The hydrofluoric acid was always care- 
B---=-4 fully removed by washing and then drying the 
tubes before using the sealing wax. Or the tubes 
may be fastened gas-tight together by means of 
FIG. 2. Method Htharge and removed, when desired, by nitric 
of making glass tube acid as was done by Pfeffer.t One tube, A, had 
connections by on its inner end, at C, a few layers of compact 
area: oF Gifelaey filter paper so as to make it fit B tightly. Ne 
finely powdered sealing wax was then sif ted in be- 
tween A and B from C to D. Then, on gently heating the tubes 
from C to D in a flame the powdered sealing wax was carefully 
melted, and when it was cooled there was produced an absolutely 
tight connection. When it was desired to disconnect the tubes 
joined by sealing wax, the joint was gently heated to soften the 
wax, when the tubes were easily drawn apart. The joints made 
as above described were perfectly tight even when tested in water 
by a pressure of about one half an atmosphere. The U-tubes 
can be so arranged as to be totally under water as shown by 
Ewart.t 2 
A more simple and convenient way is to test the various joints 
by means of the large, short glass tube shown in FIG. 3. Each en 
of the large glass tube is closed by a split cork to hold the apparatus 
* Andrews, loc. cit. 523. 
T Pfeffer, W. Osmotische Untersuchungen 7, 12. 1877. 
+ Ewart, A. J. Protoplasmic streaming in plants 41. 1902. 
