REMOVAL OF CALCIUM FROM THE TISSUES 315 



the whole animal, minute doses are applied to the White matter of the 

 Cerebellum, by direct injection below the gray matter of the surface. 

 The convulsive effects of large doses are therefore attributable to 

 excitation of the white matter of the cerebellum. Chronic ingestion 

 or injection of calcium precipitants leads to partial solution of the bones 

 which become thin and soft, a condition not infrequently met with in 

 sheep that have been feeding for some time upon plants of the Oxalis 

 group. The effects of calcium precipitants in the order in which they 

 occur are therefore: 1. Purgation. 2. Peripheral muscular twitchings 

 and diuresis, 3. Cerebellar excitation. 4. Partial solution of the bones. 

 A measure of Tolerance to the first three groups of effects is developed 

 after repeated administration. 



The variety of sensitiveness and response of differing tissues to 

 modifications of the inorganic environment is again displayed in these 

 effects. The very striking instance of the varying sensibility of differ- 

 ent cells to this type of environmental disturbance is afforded by the 

 complete insensitiveness of the Gray Matter of the central nervous 

 system to calcium precipitants. We have noted above that the cere- 

 bellar effects of calcium precipitants are only elicited when the salt 

 reaches the white matter of the cerebellum, and Maxwell has shown 

 that solutions of the various calcium precipitants are without effect 

 when placed upon the surface of the motor-area of the cerebrum, but 

 immediately induce convulsions when they penetrate by diffusion or 

 injection to the underlying white fibers. 



The origin of the purgation by the Saline Cathartics has been the 

 subject of much and prolonged discussion. The earliest suggestion 

 was that made by Poiseuille and Liebig, to the effect that the action 

 of these cathartics was a purely osmotic one; the excess of salt within 

 the intestinal cavity withdrawing water from the tissues and tissue- 

 fluids, while the tension of the intestinal musculature caused by this 

 collection of fluid within the lumen of the intestine led to rapid expul- 

 sion of the contents. The great French Physiologist, Claude Bernard, 

 however, showed that the intravenous injection of sulphates caused 

 purgation, although the osmotic effect in this instance should be the 

 reverse of that imagined by Poiseuille and Liebig, and water should 

 be withdrawn from the intestine into the circulation. To meet this 

 objection a modification of the osmotic theory was subsequently 

 brought forward by Wagner and Schmiedeberg, who suggested that 

 the saline cathartics modify the Permeability of the intestinal epithe- 

 lium, in such a manner that the absorption of water from the intestine 

 is hindered and the fluidity of the contents and distention of the mus- 

 cular walls, which ensues from the accumulation of unabsorbed fluids, 

 leads to the rapid evacuation of fluid feces. 



The discovery by Loeb that those salts which increase the -^ ratio, 

 and especially those which precipitate calcium, induce hyperirri- 

 tability in muscular tissues, at once threw a new light upon the action 

 of the saline cathartics. A large proportion of these cathartics are 



