200 ESSENTIALS OT? CHEMICAL PHYSIOLOGY 



Press a small piece between two glass slides and place it in front of the spec- 

 troscope. Observe and map out the bands of myohaematin. This pigment is 

 doubtless a derivative of haemoglobin. 



(d) Pieces of the same muscles have been placed in ether for twenty -four 

 hours. The ether dissolves out a yellow lipochrome from the adherent fat. 

 A watery fluid below contains modified myohaematin. Filter it ; compare 

 its spectrum with that of haemochromogen. The myohaematin bands are 

 rather nearer the violet end of the spectrum (fig. 61, spectrum 2) than those 

 of haemochromogen (tig. 57, spectrum 9). 



11. Creatine : 



(a) Take some of the red fluid described in 10, d, and let it evaporate to 

 dryness in a/ desiccator over sulphuric acid (fig. 62). 



In a day or two crystals of creatine tinged with myohaematin separate out. 



(b) Take an aqueous extract of muscle, like Liebig's extract or beef-tea ; 

 add baryta water to precipitate the phosphates, and filter. Kemove excess 

 of baryta by a stream of carbonic acid ; filter off the barium carbonate and 

 evaporate the filtrate on the water-bath to a thick syrup. Set it aside to cool, 

 and in a few days crystalline deposits of creatine will be found at the bottom 

 of the vessel. These are washed with alcohol and dissolved in hot water. 

 On concentrating the aqueous solution crystals once more separate out, 

 which may be still further purified by recrystallisation. 



NERVOUS TISSUES 



The chemical investigation of nervous tissues is not well adapted to 

 class exercises ; still it may not be uninteresting to state briefly the princi- 

 pal known facts in relation to this subject. The most important points 

 which any table of analysis will show are : (1) the large percentage of water, 

 especially in the grey matter ; (2) the large percentage of protein. In grey 

 matter, where the cells are prominent structures, this is most marked, and 

 of the solids, protein material here comprises more than half of the total. 

 The following are some analyses which give the mean of a number or 

 observations on the nervous tissues of human beings, monkeys, dogs, and 

 cats : 



The most important protein is nucleo-protein ; there is also a certain 

 amount of globulin, which, like the paramyosinogen of muscle, is coagulated 

 by heat at the low temperature of 47 C. A certain small amount of neuro- 



