286 VENOMOUS SNAKES AND THE PHENOMENA OF THEIR VENOM 



Weir Mitchell l made a similar experiment in 1859 and obtained results 

 which tend to show that the effects observed by Salisbury were caused by the 

 mechanical injuries from the insertion of the instrument. He experimented 

 first with active crotalus venom on four young shoots of Tradescantia, a very 

 succulent and tender trailing plant. Each of the shoots was split half-way 

 through, and about a third of a grain of dry, pulverized venom was dropped 

 into the opening, which was then allowed to close on the poison. Next the 

 plants were well watered and a drop or two allowed to fall on the line of 

 incision. Four controls were made without venom. During a week no 

 result was obtained. After that period two of the unvenomed shoots and 

 one of the poisoned became sickly and gradually lost most of their leaves 

 within the ensuing fortnight. 



In his second series of experiments Mitchell employed (i) a young shoot 

 of common bean; (2) a long flower or budding flower-stalk of medicinal 

 colchicum, C. autumnale; (3) three branches of geranium, growing on a 

 large and healthy plant; (4) a small succulent garden weed; (5) a young 

 dahlia. The venom was freshly collected and had been tested for its potency 

 on animals. The mode of introducing the venom varied according to the 

 kind of plant, but it was accurate and reliable, the quantity of venom being 

 one or two drops. Unfortunately some of the plants had no controls. The 

 period of observation was three weeks, but neither in the bean, colchicum, or 

 geranium did the leaves die or the plants suffer in any way. Mitchell, how- 

 ever, reserved any definite conclusion as to the effect of venom on higher 

 plants in general. 



One of the most interesting experiments is the inhibiting influence of cro- 

 talus venom upon germination of seeds of certain plants. Mitchell placed 

 a number of the seeds of canary and mignonette in venom solution (i or 0.5 

 drop of fresh venom to 8 drops of water) and in plain water. None of the 

 seeds in the venom solution germinated, while germination took place in plain 

 water under otherwise similar circumstances. 



C. Darwin 2 observed that 0.015 m - f cobra venom dissolved in 8 c.c. of 

 water acted powerfully on Drosera. A minute drop on a small pin's head 

 acted energetically on several glands, more powerfully than the fresh poison 

 from a viper's fang. Three leaves were immersed in 90 minims of the solu- 

 tion; the tentacles soon became inflated and the glands quite white, as if they 

 had been placed in boiling water. After 8 hours' immersion they were taken 

 out and placed in a fresh lot of water, and after about 48 hours re-expanded, 

 showing that they were by no means dead. 



1 Weir Mitchell. Smithsonian Contr. to Knowledge, 1861, Washington, D. C. 



2 Quoted by Brunton and Fayrer. Proc. Roy. Soc., 1875, 273. 



