55 



XIV 



196. An examination of some of the more important tis- 

 sues of the body. 



197. Saline extract of Nervous Tissue. This may be 

 made by triturating the cerebrum with 5% magnesium sul- 

 phate in a mortar. After filtering the extract may be used in 

 the following tests. The solids of a salirie extract of the 

 brain are derived chiefly from the gray matter, nerve cells. 



198. Apply the xanthoproteic test to a portion of the 

 above extract. 



199. Faintly acidify another portion with acetic acid and 

 boil. If coagulated a proteid is present. This may be a 

 native albumin or globulin or both. 



200. An ethereal extract of the brain or cord contains 

 solids derived chiefly from the white matter (nerve fibers). 



201. Pour out a little ethereal extract of brain upon 

 paper and note that there is a permanent greasy stain, indi- 

 cating the presence of fat. Remember that this is not wholly 

 ordinary fat, but largely a nitrogenous, phosphorated fat — 

 lecithin. 



202. To another portion add, very cautiously, some strong 

 sulphuric acid. If a cherry red color results at the junction 

 of the fluids it denotes the presence of cholesterin. Make a 

 control test by putting a little ether in a test-tube and adding 

 some strong sulphuric acid. No red color should appear. 



203. Saline extract of Liver. (10% NaCl). Divide the 

 fluid into three portions. 



204." To one portion apply the xanthoproteic test. 



205. Faintly acidify another portion with dilute acetic 

 acid and boil. If coagulated it indicates native albumin or 

 globulin or both. 



206. Saturate the third portion with magnesium sulphate. 

 A precipitate should occur of a proteid character. The 

 proteid may be globulin and partly nucleo-albumin. 



207. Filter the mixture obtained in 206. Boil the filtrate. 

 Little or no coagulation may occur, indicating little or no 

 albumin in the filtrate. 



