LESSON XXII 

 MUSCLE AND NERVOUS TISSUE 



1. Hopkins's Lactic Acid Test (see p. 185) may be applied as follows. Remove 

 one hind limb of a pithed frog. Stimulate the sacral plexus of the other side 

 for ten minutes with a strong Faradic current. Then amputate the other 

 hind limb. Skin both legs, and chop up the muscles of the two sides 

 separately. Pound each in a mortar with clean sand and then with 15 c.c. 

 of 95-per-cent. alcohol. Transfer the mixture to a beaker, and warm in the 

 water-bath for a few minutes. Filter, and evaporate the filtrate to dryness 

 in a water-bath. Extract the residue with about 5 c.c. of cold water, rubbing 

 it up thoroughly with a glass rod. Filter and boil the nitrate in a test-tube 

 for about a minute with as much animal charcoal as will lie on a threepenny- 

 piece. Filter again arid evaporate the filtrate to dryness in a water-bath. 

 Allow the residue to cool, and dissolve it by shaking in 5 c.c. of concentrated 

 sulphuric acid. Transfer this to a dry test-tube ; add three drops of 

 saturated solution of copper sulphate, and place the tube in boiling water 

 for five minutes. Cool and add 2 drops of 0'2-per-cent. solution of thiophene 

 in alcohol ; replace the tube in the boiling water. A cherry-red colour 

 develops in the tube containing the extract from tetanised muscle, but not 

 in the other. 



2 A rabbit has been killed and its muscles washed free from blood by a 

 stream of salt solution injected through the aorta. The muscles have been 

 quickly removed, chopped up small, and extracted with 5-per-cent. solution 

 of magnesium sulphate. This extract is given out. It will probably be 

 faintly acid. The acid is sarco-lactic acid. It may be identified by 

 Uffelmann's (p. 185) or Hopkins's reaction. 



3. The coagulation of muscle is very like that of blood. This may be 

 shown with the salted muscle plasma (the extract given out) as follows : 

 Dilute some of it with four times its volume of water ; divide it into two 

 parts ; keep one at 4CP C. and the other at the ordinary temperature. Co- 

 agulation that is, formation of a clot of myosin occurs in both, but earliest 

 in that at 40 C. 



4. Remove the clot of myosin from 3 ; observe it is soluble in 10-per- 

 cent, sodium chloride, and also in 0'2-per-cent. hydrochloric acid, forming 

 syntonin. 



5. Make an extract of muscle in the same way, using a small quantity 

 of physiological salt solution instead of the strong solution of magnesium 

 sulphate employed in the foregoing experiments. Such an extract contains 

 the two principal muscular proteins, viz. paramyosinogen (v. Fiirth's myosin) 



