6O W. M. BALDWIN. 







longer than twenty-four hours. Cultures of the paramcecia 

 were added to graded dilutions of the stain with the object of 

 ascertaining the maximum degree of concentration compatible 

 with the life of the organism. The absorption of the stain by 

 the organism was demonstrable through the appearance of stained 

 globules within the body. It was ascertained early in the experi- 

 ment that this absorption would progress, if undisturbed, to such 

 a degree that the death of the organism resulted. When this 

 phenomenon was about to ensue the motility of the organism 

 became very sluggish, finally ceasing altogether. The elongated, 

 elliptical body-shape was replaced by a spherical form, while the 

 nucleus quickly became deeply stained. It was found not to be 

 possible to bring about a staining reaction of the nucleus without 

 causing the death of the organism. Indeed, the latter became a 

 safe index of over-absorption of the stain. 



For the purpose of testing out the absorption capacity for the 

 stain compatible with the life of the organism, 0.5 c.c. cultures 

 of the paramcecia were placed in ordinary watch glasses, to which 

 were added varying amounts of the solutions of the stains. 

 In the preliminary experiments these proportions ranged from 

 two volumes of culture to twelve volumes of stain, to eight 

 volumes of culture to two of stain. The cultures were then 

 carefully attended during the succeeding days with the view of 

 providing sufficient oxygen and to prevent evaporation. A 

 reference to a typical experiment of May 31, 1916, A.M., will be 

 sufficient to give an exact idea of this procedure. For this 

 experiment a stock solution of neutral red in the strength of 

 o.ooi gm. of the dry stain of 200 c.c. water was used. 



With such stains as methylene blue and dahlia the absorption 

 capacity of the organisms was so great that it was difficult 

 even in greatly diluted solutions to prevent the staining of the 

 nucleus. With trypanblau, neutral red, and trypan red, on the 

 other hand, the capacity of the organisms for the stain seemed 

 to have a more definite though not absolutely fixed limit. In 

 these instances it was ascertained that, when the cell-body had 

 taken up its maximum carrying amount of the stain, not injurious 

 to the activity of the organism, subsequent immersion over a 

 relatively long period of time in a very greatly diluted solution 



