THE VOLATILE PART OF PLANTS. 9? 



to illustrate the peculiarities of this substance, and to ex- 

 hibit the deportment of the albuminoids generally towards 

 the above-named reagents. 



EXP. 42. Beat or whip the white of an egg so as to destroy the deli- 

 cate transparent membrane in the cells of which the albumin is held, 

 and agitate a portion of it with water ; observe that it dissolves readily in 

 the latter. 



Exp. 43. Heat a part of the undiluted white of egg in a tube or cup 

 at 105 F.; it becomes opaque, white, and solid, (coagulates) and is convert- 

 ed into the insoluble modification. A higher heat is needful to coagulate 

 solutions of albumin, in proportion as they are diluted with water. 



EXP. 44. Add strong alcohol to a portion of the solution of albumin 

 of Exp. 42. It produces coagulation. 



EXP. 45. Observe that albumin is coagulated by dilute acids applied 

 in small quantity, especially by nitric acid. 



EXP. 46. Put a little albumin, either soluble or coagulated, into each 

 of four test tubes. To one, add solution of iodine ; to a second, strong 

 chlorhydric acid ; to a third, nitric acid ; and to the last, nitrate of 

 mercury. Observe the characteristic colorations that appear immedi- 

 ately, or after a time, as described above. In the last three cases the 

 reaction is hastened by a gentle heat. 



Albumin occurs in the soluble form in the blood, and in 

 all the liquids of the healthy animal body except the urine. 

 In some cases its characters are slightly different from 

 those of egg-albumin. The albumin of the blood, which 

 may be separated by heating blood-serum (the clear 

 yellow liquid that floats above the clot), contains a little 

 less sulphur than coagulated egg- albumin. In the crystal- 

 line lens of the eye, and in the blood corpuscles, the al- 

 bumin has again slightly different characters, and has been 

 termed globulin. Under certain conditions the blood of 

 animals yields a substance known as haemoglobin, which, 

 while having nearly the composition and many of the 

 properties of albumin, commonly requires a much larger 

 proportion of water for solution, and forms distinct crys- 

 tals of a transparent red color. 



Vegetable Albumin. In the juices of all plants is found 

 a minute quantity of a substance which agrees in nearly 

 all respects with animal albumin, and is hence termed 

 5 



