Experiments on Permeability of Cells. 



127 



Fig. 3. 



in these experiments all toxic substances were eliminated from the water by redistilling 

 it in the apparatus shown in figure 3. The stock bottle (to the left) is filled with distilled 

 water, which siphons over into the beaker and keeps the latter filled up to the mouth of the 

 wide tube. A small flame under the beaker boils the water and drives out all dissolved gases 

 (since the water contains no salts to hold back CO2, and no non-volatile substances to 

 liberate ammonia). The boiling water from the beaker siphons over into the Kjeldahl 

 flask over a large flame. If the siphon be drawn out into a fairly small opening the Kjeldahl 

 flask may be set lower than the beaker, as in the figure; but this has the disadvantage that 

 when the still is cooled the Kjeldahl flask fills up to the neck and makes it inconvenient 

 to start again. The siphon has a bulb blown on it at a, to stop the mouth of the flask. 

 It is not necessary that this stopper be ground in, provided it fits fairly snug, as water 

 condenses on the stopper and seals the crack. A hole is blown in the side of the neck of 

 the flask to admit the condensing tube. This hole may be reamed out with the end of the 

 tube itself, while the glass is hot, to insure a fairly close fit. The condensing tube is of 

 fused quartz and the only water that collects in the receiving bottle is condensed on the 

 quartz. The cold water dissolves glass very slowly, so that it is permissible to use a glass 

 receiving bottle if the water is distilled fresh each day. Hard glass (Jena or Bohemian) 

 dissolves more slowly but contains heavy metals which are toxic even in the minute quanti- 

 ties that dissolve away in the cold distilled water, even though the glass be previously 

 steamed out. Soft glass liberates traces of sodium, calcium, and potassium, which render 

 the water less toxic, but which, if present in sufficient quantity, may be a source of error 

 in the experiment. 



In a previous paper ^ I concluded that the fertiHzation membrane is the 

 result of a mutual coagulation and precipitation between the jelly and 

 another transparent colloid filling the space between it and the egg. I 

 found that if the jelly be removed from the egg no fertilization membrane 

 can be formed. Elder- subsequently made the same observation and came 

 to the same conclusion. No matter what is the nature of the membrane, 



' McClendon. Science, vol. 33. P- 387. Mar. 10, 191 1. '^j-ch.f. Entwicklungmech., vol. 33. p. 143. 1912. 



