300 
submerged. The actual temperature to which the cells were exposed 
was recorded by especially arranged thermometers. Without here 
recounting the entire series of observations, the details of two ex- 
periments will be given. 
A. Preparation, prepared as above, was placed in cold-chamber 
at a temperature of 7—8° C. 
After 4 days, 7 hours: examination shows many cells still 
actively moving; replaced in cold-chamber. 
After 6 days, 7 hours: cells at first motionless; on lying for a 
few minutes in the temperature of the laboratory, about 24° C, 
many cells exhibited lively motion. Replaced in cold-chamber. 
After 7 days, 9 hours: at first no motion, but revived after lying 
fifteen minutes at 24° C. Replaced in cold-chamber. 
After 8 days, 10 hours: no motion for some time, but later, after 
exposure to 25° C for two hours, a few cells displayed feeble 
movement. Observation discontinued. 
Control preparation kept continuously at 21° C exhibits motion 
only to the end of the fourth day. 
B. Preparation prepared as before; subjected to temperature of 
8,590: 
After 5 days, 5 hours: examination shows a few cells still 
moving; on lying forty-five minutes at 24° C, every lively 
motion in very many cells. Replaced in cold-chamber. 
After 6 days, 6 hours: no motion at first; on lying one hour at 
25° C, entire fields of actively moving cells. Re- 
placed in cold-chamber. 
After 8 days, 8 hours: on lying one hour at 25° C, still many 
cells showed vigorous movement. Replaced in cold-chamber. 
After 9 days, 9 hours: on keeping preparation at 25° C for one 
hour, a few cells exhibit well marked motion. Observation 
discontinued. 
It is of interest to note, that the capability of moving was much 
more prolonged in those cells in which vibration was temporarily | 
arrested, from time to time, by the reduced temperature than in the 
cells of the control preparations in which the spermatozoa were conti- 
nuously in action at a temperature of about 24° C, a fact which may, 
possibly, find a parallel in the less rapid exhaustion of contractility 
in a muscle fibre when periods of rest alternate with those of activity. 
This prolonged capability of movement of human spermatozoa — 
the possibility of such vibration existing after the expiration of nine 
days being thus directly established — still further emphasizes the — 
