SALT AND ITS PHYSIOLOGICAL USKS. 5G7 



chain of iirg-umcnt. Therefore the principle of this theory is uncer- 

 tain and may ))C contested. Indeed, it has l)een. 



It is pt)ssil)h\ conti'ary to the reasoning of Bung-e, to increase the 

 rehitive and absolute quantity of potash taken into the system with- 

 out increasino- the appetite for salt: indoed. we may even decrease the 

 desire foi' it. 



An example of this sort is found among the negro tribes of Africa 

 who use '\/.s7/ .^aU.'^ The use of this mineral condiment extends 

 throughout a large part of central Africa in the basins of the Ogove 

 and Sanga north of the Congo and in the provinces of the Free State 

 to the south on the opposite side of the river. The lack of sea salt 

 or rock salt causes these populations to replace this substance l)y 

 another saline material which they prepare on the spot by their own 

 means. 



But tliis is not ordinarv salt — chloride of sodium; it is not even a 

 soda salt. They ol)tain this spurious salt from the ashes of plants. 

 Not the first that come to hand, for it is not immaterial w'hat plants 

 are chosen for this purpose. On the contrary, they are carefull}' 

 selected species. The}' use particularly two plants from the river. 

 The favorite one is a floating aroid common on the Ogove and deter- 

 mined by M. Lecomte as the Pidia dratiotes. It is said that at cer- 

 tain places this plant is cultivated solely for the purpose of extracting 

 its salt. The second is a sort of high ban)boo that grows in clumps 

 upon iiuindated ban':s. 



What peculiarity have these plants that causes them to be chosen to 

 the exclusion of others? We do not know. M. L. Lapicque, from 

 whom we have derived a part of this information, supposes that it is 

 the slight proportion of carl)onates that the}' furnish when incinerated, 

 or as the effect of sulisequent treatment. In a product destined for 

 food, the lack of alkaline carbonates is a decided advantage, for their 

 nauseous odor and alkaline taste is repulsive to all. 



Aftei' being harvested the plants are dried and then burned; the 

 ashes are collected and leached. At Berberati, on the Upper Sanga, 

 Dr. Herr witnessed this process. The aborigines use for this purpose 

 a rude hlter made of a conical basket, in which the ashes are placed. 

 Through this water is passed and repassed several times to dissolve out 

 all the soluble salts. The solution thus obtained is then evaporated 

 l)y heat. The tixed residue forms the ^^ axJt sa/t.'' 



The composition of this salt, at least as to its general features, is 

 well known. M. Dybowski, in 1893, comnuuiicated to the Academy 

 of Sciences some analyses of it. Its composition varies little from 

 that furnished by most plants similarl}^ treated. Normally, as has 

 been already said, potash is greatly in excess of soda in all vegetables. 

 The proportion varies from 3(» tp 150 parts of potash to 1 of soda. 

 i'hat is what we find in this case; the cpiantity of soda is verj' minute. 



