90 SOLUTIONS AND PROTOPLASM [Cn. Ill 



the repulsive quality varies with the quality of the substance 

 may occur even in substances which are not attractive at 

 any concentration. PFEFFER is, therefore, inclined to regard 

 strong, repelling solutions as acting in a different fashion from 

 attractive ones. Just as strong sunlight may repel organisms 

 attracted by weak light, both phenomena being light phe- 

 nomena, so the repulsion and attraction of solutions may 

 both be regarded as chemical phenomena. 



The work of MASSART brought evidence against PFEFFER'S 

 conclusions, and added many important data. His studies 

 were made chiefly upon bacteria, to a less degree upon Flagel- 

 lata, Hydra, the frog, and the human conjunctiva. The results 

 of the studies showed that neutral solutions of a certain con- 

 centration repel, and that the repulsion is proportional to their 

 isotonic coefficients and inversely proportional to their molecu- 

 lar weights, and, therefore, that the repulsions are purely 

 osmotic phenomena. 



The conclusions of MASSART thus summarized were obtained 

 by the use of special methods, which gave quantitative results. 

 So they are worth detailed consideration. A drop of liquid 

 containing bacteria is suspended from the under side of a 

 cover-glass in a moist chamber whose side walls are formed of 

 cardboard, and whose top is the cover-glass. Into the drop, 

 glass capillary tubes similar to those used by PFEFFER are in- 

 troduced, filled with the solution whose action is to be studied. 

 In addition to this solution all the tubes should contain YO/W^ 

 MW % (0.00691 gr. %) K 2 CO 3 for the purpose of attracting 

 the bacteria. When a tube containing only this dilute solution 

 of K 2 CO 3 is put into the drop, bacteria crowd into it and liter- 

 ally fill it in from 20 to 30 minutes. But when a series of 

 increasing solutions of a neutral salt like NaCl is added to the 

 K 2 CO 3 , the organisms at first do not crowd in so rapidly, then 

 remain at the mouth, and, finally, are repelled from the tube 

 opening. MASSART has tabulated the results obtained with 

 Spirillum upon using tubes containing different chemical sub- 

 stances in different degrees of concentration. One of these 

 tables, in slightly modified form, is reproduced here. In this 

 table, A indicates that the bacteria entered the tube readily ; 

 a, that they merely gathered about its mouth ; 0, that they 



