CHEMISTRY OF THE BODY 105 



LABORATORY EXPERIMENTS ON THE CHEMISTRY OF THE 



BODY. 



This list will serve as basal for the guidance of students and teachers. 

 The experiments listed are to be supplemented by technical laboratory 

 guides and references to fuller discussion in the literature. 



THE PROTEINS. 



i. Preparation of Proteins. The most convenient source of proteins 

 for laboratory work are blood serum, egg white, or commercial preparations 

 of the milk protein casein. Protein may also be prepared from various 

 plant seeds, especially cereals. Hempseed contains a globulin, edestin, 

 which is very easily isolated in the laboratory. 



a. Preparation of Edestin. Grind up some hemp-seed in an ordinary 

 meat chopper and extract the resulting meal with 5 per cent, salt solution, 

 warming to 60. The solution should not be heated above 65 because 

 the protein will be coagulated. Filter while hot. On cooling slowly the 

 edestin will crystallize out. Examine some of the precipitate with a micro- 

 scope and sketch the crystals. The edestin is soluble in 10 per cent, salt 

 solution without warming, and solutions for laboratory use can be prepared 

 in this way. 



b. Preparation of Egg Albumin. The yolk should be separated from 

 the white of fresh eggs and the reticulum in the egg white broken up with 

 a wire egg-beater. Egg white can then be diluted as desired and the pre- 

 cipitate globulin filtered off. Crystals of ovalbumin can be prepared as 

 follows: 



The egg white, beaten as directed, is strained through gauze and an 

 equal volume of saturated ammonium sulphate solution is added. After 

 twenty-four hours the globulin precipitate is filtered off and concentrated 

 ammonium sulphate solution added until the mixture becomes turbid. 

 Then distilled water is added very carefully until turbidity has disappeared. 

 The solution is then acidified with acetic acid, which has been saturated 

 with ammonium sulphate, until a precipitate is obtained." The precipitate 

 is at first amorphous, and on standing becomes crystalline. Examine the 

 crystals under the microscope and sketch them. 



c. Other Protein Crystals. Crystals of hemoglobin may be demon- 

 strated by adding a drop of ether to diluted dog blood on the microscope 

 slide and allowing the mixture to dry around the edge. Hemoglobin crys- 

 tals may be observed under the microscope to have formed where the solu- 

 tion has concentrated and dried. 



Crystals of seralbumin and of lactalbumin can be obtained in essen- 

 tially the same manner already described for ovalbumin. 



