12 



BULLETIN 1023, U. S. DEPARTMENT OF AGRICULTURE. 



The only conceivable advantages in the use of a preparation of this 

 sort are its highly probable nonabsorption in the stomach, and the 

 absence from it of taste. Presumably the rat would receive no imme- 

 diate physiological Avarning, since no strychnine would be liberated 

 to be absorbed by the stomach. The amounts which would be surely 

 lethal, however, are large and the cost of the commercial article is 

 so great that the practicability of its use for rats is open to question 

 at present. 



Table 7. — Toxicity of strychnine sulphate diatomaceous earth preparation to 



wild rats. 



Number of rats. 



Weight. 



Dose of 

 strych- 

 nine sul- 

 phate 

 per kilo. 1 



Sur- 

 vivals. 



Fatal- 

 ities. 



Mor- 

 tality. 



8 



Grams. 

 126 to 328.... 

 186 to 192.... 

 105 to 360.... 

 130 to 136.... 

 234 to 300.... 

 93 to 300 



Milligrams. 

 10 

 20 

 25 

 35 

 40 

 50 



28 

 32 

 «4 



1 



4 





Percent. 



2 







5 



< 1 

 •'■>2 

 U 



65 



20 



2 



100 



2 



50 



9 



55 







1 Material was suspended in starch paste so as to contain 1.0 per cent of the alkaloidal salt. . 



2 Only 2 were spastic. 



3 Both were nervous. 



4 All were spastic. 



5 Fatalities occurred after second hour. 



6 Five died within 24 hours. 



EFFECT OF AGE OR DEVELOPMENT UPON TOXICITY OF STRYCHNINE. 



In experiments reported elsewhere (25) it has been shown that 

 as the rat develops it passes through stages indicating in a functional 

 way the development of its nervous system. Early during the nurs- 

 ing or crawling stage the tolerance to strychnine is high. There 

 is also a latitude between the minimum convulsive and the minimum 

 lethal subcutaneous dose. By the time the animal acquires some 

 physical dexterity the lethal dose falls to about the level of the 

 convulsive dose. These rats then have only a few spasms pre- 

 ceding death, while in the crawling stage when a lethal dose is 

 administered many spasms usualty occur. About the time the rat 

 is capable of beginning an independent existence (25 days) the 

 resistance begins to rise, and ordinarily no convulsions occur until 

 the lethal dose is reached. The highest subcutaneous dose survived 

 by the rats in the crawling stage is 2 milligrams per kilo. Just after 

 this stage is passed (in the weaning stage) the lethal dose is ap- 

 proximately 0.5 milligram per kilo. At about the time of sexual 

 maturity it is 3 milligrams per kilo, or six times that of the weaning 

 stage tolerance. 



DISPOSAL OF STRYCHNINE. 



In a series of experiments reported in detail elsewhere (26), it was 

 found that the rat can always dispose of 33 per cent of a minimum 

 lethal subcutaneous dose of strychnine in two hours; that about half 



