TOXICITY OF BAKIUM CARBONATE TO RATS. 3 



Unfortunately, in some cases, exact lethal and sublethal doses are 

 not known, since the amounts administered have not been based 

 upon body weight. In other instances it has been necessary to 

 calculate some of the figures from the authors' data. It would 

 appear, however, that rabbits, chickens, and pigeons are about 

 equally susceptible to barium administered subcutaneously, while 

 cats and dogs are approximately three times as sensitive. Owing to 

 differences in the physiology of the stomachs of the different species, 

 and presumably to the differences in the average size between species, 

 the toxicity of barium by mouth varies markedly, the purely species 

 characteristic becoming more or less masked. For practical pur- 

 poses, however, it may be assumed that the lethal dose of barium 

 per os per kilo tends to decrease relatively as the size of the animal 

 increases. 



EXPERIMENTAL PROCEDURE. 



In the experiments here reported the brown rat (Rattus norvegicus) 

 was used as often as practicable. The domesticated white strain 

 was employed for obtaining accurate food-intake data and for testing 

 the relative efficiency of different percentages of barium carbonate in 

 the bait. The melanotic strain was used in only a few toxicity ex- 

 periments for purposes of comparison. The substitution of the white 

 rat for the brown strain would seem fair, since the toxicity of barium 

 to these two strains was found to be the same. The feeding experi- 

 ments were confined, as far as possible, to the laboratory phase, 

 although at times it was necessary to consider in some detail the 

 practical aspects. In the experiments in which the stomach tube 

 was used, the animals were first anesthetized with ether. The 

 lethal doses are regarded, not as the minimum amounts which might 

 be fatal, but those amounts which will kill a large proportion of the 

 rats. 



The barium chlorid administered was the ordinary crystalized salt 

 (BaCl 2 -2H 2 0). The carbonate, which was of high purity and free 

 from soluble chlorid, was always used in the form of fine powder, hav- 

 ing been passed through a 100-mesh sieve. The molecular weight and 

 barium content of these preparations are given in Table 3, since their 

 relative toxicity is determined on the basis of their barium content. 



Table 3. — Molecular weight and barium content of barium chlorid and barium carbonate. 



Salt. 



Molecular 

 weight. 



Barium. 



Conversion 

 factor of 

 barium 

 into salt. 



BaCl 2 -2Uo0.. 

 BaC0 3 ---.-. 

 Ba 



244. 32 



197. 37 



i 137. 37 



Per cent. 

 56.2 

 69.6 



1.778 

 1; 437 









1 Atomic weight. 



