De er Oe 
1900-1901.| Experiments on the Growth of Yeast. 207 
yeast in a solution of glucose alone, and in similar solutions of 
glucose containing weak, medium, and strong doses of arsenious 
oxide. The quantity of CO, given off is shown by the 
ordinate, and the time is indicated along the abscissa. Simi- 
larly, in Plate XXVI. a curve is given for each flask. Plate 
XXVII. shows at the end of each day the action in the 
different flasks. 
Now, as to the things to be noted from our experiments, we 
would mention several. It is too early to draw conclusions. 
1. It must strike every one that a simple organism—an 
organism consisting of a single cell like yeast—can live in a 
very strong arsenical solution, while a minute dose would 
poison a man. The beer which poisoned those who drank it 
at Manchester contained 1:4 grains per gallon—ze., 1 in 
50,000. Some of the poisoned drank more than a gallon per 
day, others did not take more than a pint.’ If we consider 
2 or 3 grains as a certainly fatal dose for man, and a man 
weighs, say, 200 lb., -5alpo of his weight is a poisonous dose. 
If we consider yeast to be roughly of the same specific gravity 
as water,—and in one of our experiments we used a solution of 
1 in 500, so that yeast can live in =4, of its weight of 
arsenic, that is a thousand times as much as a man,—that 
was to be expected. In the complex tissues of the higher 
animals drugs affect certain cells or tissues more than they 
do others. That is the case with arsenic, and we believe we 
are right in saying that it is the basis of medicine. 
2. Some curious and exceedingly interesting experiments 
were made a dozen years ago by Hugo Schultz on simple 
animal and vegetable cells by treating them with exceedingly 
dilute solutions of virulent poisons. The experiments are 
recorded in Pfliiger’s ‘ Archiv’ for 1888. Schultz used cor- 
rosive sublimate, iodine, formic acid, arsenious oxide, chromic 
acid, and some other reagents, and he found the activity of the 
organism at once increased. He measured the quantity of 
carbon dioxide given off by manometers of simple construction, 
and he made readings after the addition of the poison every 
two hours, if we remember correctly. The advantage of using 
his method is that results are easily read off. 
Reaction to a stimulus—an irritation—is the most character- 
1 ‘Nature,’ 4th April 1901. 
