1910.] 



produced hy Animal and Vegetable Life. 



G43 



was thought that bacteria could be found to satisfy the conditions equally 

 well, ill spite of the difficulty of observing them readily, but in any loopful 

 tliere are liable to be inert organisms which confuse the result. Many 

 observations were, however, made with blood corpuscles and bacteria mixed 

 in a drop of tap water or weak saline solution. When the latter were fresh 

 the etfect was marked, the blood cells of both kinds moving actively to the 

 positive, the bacteria to the negative, streaming past one another, stopping, 

 starting, and reversing with the current. 



For the purpose of demonstration the difficulty was to find a vegetable 

 growth of great vigour with single non-motile cells of convenient size for 

 observation. This was eventually found in Torula. Yeast is easily obtained 

 and complies with all the requkements. Blood and yeast cells are of the 

 same size, but the slight colour of the former and the oval shape of the latter 

 enable them to be readily distinguished. Judging by the velocity of 

 migration the charge carried is of the same order in each. In a field contain- 

 ing many of both kinds they move past each other and after collision pass on 

 with unchanged speed. The effect can be readily projected upon a screen with 

 arc light, using a No. 6 objective well stopped down, the disc obtained being 

 about 3 inches in diameter. It is unlikely that the electrical charges reside 

 only on the surface, for they would, at least in part, coalesce, as they do in 

 neutralised colloidal solutions.* The charges of blood and yeast cells appear 

 also to be exceedingly stable. Smears of either on glass, dried for several 

 days, on being moistened with water exhibit the effect quite well. 



It may then be reasonably concluded, in so far as it is possible to have a 

 single crucial test for so wide a range of activities, that fresh animal cells are 

 negatively, and vegetable cells positively electrified. The fact that collisions 

 do not discharge the cells, and that in both kinds the reversal of charge 

 (which has no doubt led to most of the conflicting evidence on electrical 

 migration of cells) takes place slowly, and cannot well be located in the cell 

 wall, suggests that the above conclusion may tentatively be extended to the 

 protoplasm. The principal difference between the two modes of life would 

 then be that active animal protoplasm produces negative electrification, 

 vegetable positive. Expressed in terms of Hardy's results'the former is acidic, 

 the latter basic in type. 



6. Contributory Evidence. — This conclusion is not without support from less 

 direct experiment. It has been shown by Dr. Wallerf that the local skin 

 response current is opposite in sign in animal and vegetable tissues, indicating 

 an essential difference in the normal charge of their cells. 



* "W. B. Hardy, loc. cit. 



t A. D. Waller, ' Sigus of Life,' p. 



84, § 51. 



VOL. LXXXII. — B. 



3 B 



