CRETA PREP ARATA — PREPARED CHALK 355 



tion and prolongs the period of relaxation of muscle, constricts the 

 bloodvessels and increases the rhythm and force of the heart beat. 

 These effects are antagonized by potassium and magnesium and vice 

 versa. 



One of the most important specific actions of calcium is its power 

 to retard or prevent inflammation. For instance, a calcium salt in- 

 jected subcutaneously will prevent the reaction from the application 

 of mustard, probably on account of a lessened permeability of the 

 bloodvessels. Normal dogs are resistant to the experimental pro- 

 duction of moist eczema, but if the calcium in the circulation is pre- 

 cipitated by the injection of oxalates, the resistance is reduced. 

 This has suggested the use of calcium in the treatment of moist 

 eczema and urticaria and to prevent rashes following the use of 

 serum. It is not known how this action is brought about. 



Nervous System. Calcium salts favor the normal reaction of 

 nerve tissue. Gushing demonstrated that the sensitiveness of motor 

 nerve endings which have been depressed by normal saline, regain 

 their sensitiveness by perfusion of normal amounts of calcium in the 

 saline solution. 



Absorption and Elimination. Calcium salts are absorbed to 

 a small extent from the stomach and intestines. Absorption is facili- 

 tated by the presence of fats which form calcium soaps. Most of 

 the absorbed salt is excreted into the intestine but some escapes by 

 the urine. The percentage eliminated by the urine is increased dur- 

 ing calcium starvation and is more during rest than in exercise. The 

 percentage in the blood is not influenced by oral doses to normal ani- 

 mals. 



CALCIUM 



Metallic calcium is not used in medicine. 



CRETA PREP ARATA — PREPARED CHALK 



Synonym. Drop Chalk 



Prepared chalk is a white amorphous powder, often moulded into 

 cones, odorless, tasteless, permanent in the air, almost insoluble in 

 water, insoluble in alcohol. ; 



Incompatibilities — Acids and sulphates. 



Preparations and Doses. 



Greta Preparata. H. §j — ^ij ; 30. — 60. D. gr. x — 3j ; 



0.65 — 4.0. 

 Pulvis Cretoe Compositus. Compound Chalk Powder, chalk 



30, Acacia 20, sugar of milk 50. Dose. Same as for the 



above. 

 Misiura Cretce. Chalk Mixture. Compound chalk powder 



