WITH NATIVE AND DERIVED PROTEINS. HARRIS. 80 



to the native proteins of blood, for 1$ of fat is probably held in 

 a quite invisible form in blood-plasma. This is exceeded by 

 the liver which can hold as much as 5$ of fat in a perfectly 

 transparent and invisible form; the fat, for the time being, is 

 chemically united to the tissue-proteins. Some physiologists 

 hold that during the time that carbohydrate is in the liver, it 

 is present in a protein-complex and they say that glycogen . can 

 be demonstrated chemically in liver cells before it can be 

 histologically. 



One of the latest views as regards the early fatigue of 

 muscle is that potassium salts are detatched and sent into the 

 circulation depressing the motor nerve-endings. What unloosens 

 the potassium is not yet obvious, but it appears that potassium 

 is set free. Lactic acid is similarly free in the circulation in 

 the later stages of muscular fatigue. 



That the union is ionic as regards certain inorganic sub- 

 stances is interestingly shown in the part played by calcium 

 salts in the clotting of the milk. It is known that when the 

 rennin has transformed the caseinogen into soluble procasein 

 there is no precipitation of the latter until it has formed a union 

 with calcium: a drop or two of calcium chloride now causes an 

 abundant precipitation of casein. In 1895 I showed 1 that 

 barium chloride and strontium chloride were equally efficaci- 

 ous. Here the action must be due to the divalent ions and to the 

 different ions indifferently, for certainly the anion chlorine is 

 not the causal substance. Now while this is so as regards 

 the clotting of milk, barium cannot supplant calcium medicin- 

 ally. In particular, barium chloride cannot replace calcium 

 chloride as regards efficiency in maintaining the heart's rhythm. 

 Barium is absorbed very slowly from the intestine, and when 

 so absorbed is found to be a direct stimulant of muscle-fibre as 

 distinct from nerve-fibre. J ust as barium can replace calcium 

 in the clotting of milk so it can replace it in the clotting of 

 blood. Magnesium sulphate injected into rabbits gives rise to 



1 Harris, D. Fraser : Some points in the physiological chemistry and coagula- 

 tions of milk. Pro. Roy. Soc. Edin., Session 1895-1896. 



