456 WAYLAND M. CHESTER 



stump was seen in almost all the animals observed. If the ten- 

 tacle were stimilated to contract during the first hour after cutting, 

 the nipple disappeared; but it quickly formed again when the 

 tentacle expanded. 



It was found possible by means of chemical reagents to elimi- 

 nate the muscular activity at the time when ordinarily the nipple 

 formed. The Metridium was stupefied by chloretone, under the 

 influence of which it was kept for a greater or less length of time. 

 In some experiments magnesium sulphate instead of chloretone 

 was used, but, while the inhibition of the muscles was successful, 

 the secretion of mucus was greater and the animal was not so 

 easily controlled. A few chloretone crystals were placed on the 

 surface of the water. When the tentacles ceased to respond to 

 touch, some of them were severed. The initial in-rolhng of the 

 cut edges occurred, but there was no contraction of the tentacle 

 and no formation of a nipple. In all cases, eight hours after a 

 tentacle was cut, the opening at the distal end of the stump was 

 still present and there had been neither formation of a nipple nor 

 change of color such as accompanies contraction of the tissues. 

 The opening very gradually decreased in size during this time, 

 but it was a slow radial closing with no suggestion of the nipple- 

 like form. When the cut was midway of the tentacle, complete 

 closure occurred in from ten to twelve hours. The animal was 

 left in the chloretone during the closing of the wound and then 

 returned to normal sea water. In the twelve experiments in 

 which this was done, structural closure was effected without the 

 formation of a nipple. In other experiments, when the animal 

 was returned to nonnal sea-water at some stage before complete 

 closure of the cut end, a nipple was formed upon renewal of mus- 

 cular activity. 



The third phase in wound reaction consisted in the structural 

 closure of the cut end, accompanied by the relaxation of the nipple 

 sphincter. Twelve to twenty-four hours after the nipple was 

 first formed, the end of the tentacle appeared inflated, and was 

 hemispherical in form (fig. 2) . During that time the nipple had 

 gradually disappeared, but, for a few hours after the end became 

 rounded, a white spot could be seen at the point where the nipple 



