IRRADIATION OF LIVING PROTOPLASM 



647 



times its original value. The increase in viscosity begins at the cortex 

 and travels inward. The values given above apply only to the central 

 region of the cell. 



Sea-urchin eggs respond to ultra-violet radiation by lifting off their 

 outer membrane in a reaction characteristic of the fertilization process 

 (236, 237). However, such a response does not occur (138) if the calcium 

 is first removed by the addition of the oxalate ion. It has been found (11) 

 that muscle does not show a contracture response upon stimulation with 

 ultra-violet unless calcium ions are present. Apparently, therefore, the 

 calcium ion plays a role in the effect of ultra-violet on protoplasm. 



13 

 12 

 11 

 10 

 ^ 9 

 o 8 



° 5 



<^ 4 



3 



2 



1 



"0 30 60 90 120 180 240 300 360 



Time after Exposure in Seconds 



Fig. 2. — Viscosity of the plasmasol of Amoeba dubia at varying times after ultra-violet 

 irradiation. {After Heilbrunn and Daugherty, 137.) 



This importance of calcium is more clearly indicated by the work of 

 Heilbrunn and Daugherty (137) on Amoeba. These authors irradiated 

 amoebae with a Hanovia mercury-vapor lamp. By using two species of 

 amoebae, they were able to determine viscosity change both in the main 

 mass of the protoplasm and also in the outer gelatinous envelope or 

 plasmagel. The main mass of the protoplasm (plasmasol) is first made 

 more fluid and then more viscous by ultra-violet. The effect of various 

 doses is shown in Fig. 2. An exposure of 5 sec. produced no change, 

 while 10 sec. caused a transient liquefaction. Longer exposures caused 

 liquefaction followed by a pronounced stiffening of the protoplasm. 

 The fluid stage lasted only 1 to 2 min. The gelating effect of ultra-violet 

 could be completely inhibited by immersion in sodium or ammonium 

 oxalate solution. In the oxalate the viscosity increases somewhat 



