40 THE PROTEINS. 



egg-albumin be injected into the circulation it usually 

 passes in a short time into the urine. Serum-albumin in- 

 jected in the same manner does not pass unaltered through 

 the kidneys. Serum-albumin is more easily dissolved by 

 an excess of mineral acid than egg-albumin. They differ 

 also in their coagulation-temperatures. 



Albumin may be obtained for the experiments by dis- 

 solving the commercial dry egg-albumin or serum-albumin 

 in cold water, filtering if it is not clear. From fresh eggs 

 it can be prepared by separating the albumin from the 

 yelk, being careful not to mix them. Then beat the albu- 

 min, to break up the membranes in it, mix with twice its 

 volume of water, and filter through a piece of unbleached 

 muslin. 



82. Place a moistened piece of parchment or a parch- 

 ment filter in a funnel from which the stem has been 

 broken, and hang the funnel in a beaker of water so that 

 the water rises nearly to the top. Into the parchment pour 

 a solution of egg or serum albumin with a little salt, and 

 let it stand all night. Test the outer liquid by the xantho- 

 proteic and biuret reactions for proteids. None will be 

 found, although it contains a chlorid, as shown by adding 

 silver nitrate with nitric acid, when a white curdy precipi- 

 tate of silver chlorid appears. 



83. Tie a piece of moistened parchment over the 

 mouth of a thistle tube, then fill the bulb with an albumin 

 solution and suspend the tube by a clamp, so that the bulb 

 is covered by the water in a beaker below. The liquid rises 

 in the tube above the level of that outside owing to the 

 inward osmotic pressure of the water being greater than 

 the outward one of the albumin solution. This is the 

 action that occurs when animal cells are surrounded by 

 pure water. 



