PROTECTION FROM TOXIC REAGENTS 205 



toxic substance which each individual had to remove from suspen- 

 sion in order to lower the strength below the threshold of immediate 

 toxicity. The mechanism for this removal will be discussed later. 



Another type of experiment was run with Ophioderma to deter- 

 mine whether the protective effect of the bunch was due to the fact 



TABLE XIX 



Animals Used: Planaria dorotocephala, 15-25 Mm. Long, Exposed to Action of 

 Colloidal Silver for 7 Hours, Then Washed and Transferred to Water 

 TO Which They Were Acclimated, and Examined on the Day Following 

 the Exposure 

 I. 40 planarians isolated into 10 cc. of water plus 2 drops colloidal silver 



No. Percentage 



Normal, crawling when stimulated i 2.5 



Less than half disintegrated 2 5.0 



Half and less than two-thirds disintegrated ... 4 10. o 



Two-thirds but not all disintegrated 8 20.0 



Wholly disintegrated 25 62 . 5 



II. 150 planarians in 6 lots each in 250 cc. water plus 50 drops colloidal silver 



Normal, crawling when stimulated o o 



Less than half disintegrated o o 



Half, but less than two-thirds disintegrated. . . 18 12 



Two-thirds but not all disintegrated 52 35 



Wholly disintegrated 80 53 



III. 71 planarians in three lots each in 10 cc. of water plus 2 drops of colloidal 



silver 



Normal, crawling when stimulated 63 88.8 



Normal, not crawling when stimulated i 1.4 



Head started to disintegrate 7 9-8 



Head completely disintegrated o 0.0 



IV. 75 planarians in three lots each in 10 cc. of water plus 50 drops of colloidal 



silver 

 All wholly disintegrated. 



that the bunched animals were exposed to a smaller concentration 

 of colloidal silver than were the isolated animals. Since the area of 

 the surface would affect the aeration and so affect survival values, 

 the larger numbers were placed in crystallization dishes with a diam- 

 eter of 24 cm., while the smaller bunches and the isolated animals 

 were in the usual finger bowls with a diameter of 10 cm. The essen- 

 tials of the set-up were: 



