No. 8.— CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY 

 OF THE MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD 

 COLLEGE, UNDER THE DIRECTION OF E. L. MARK, No. 229. 



Effects of radium on living substance. — II. Comparison of the sensi- 

 "" tiveness of different tissues in the dung-tvorm Allolohophora 

 foetida and in the crayfish Cavibarus affinis to 

 the beta rays of radium. 



By E. D. Congdon. 



The relative sensitiveness of different tissues of vertebrate animals 

 to beta radiations has been determined with a fair degree of exactness 

 (see Thies, :05, Lossen, :07). though contradictory results have been 

 obtained for some tissues, especially for the central nervous system. 



The worm Allolohophora foetida was taken as one of the objects 

 of exposure and the histological changes examined in twenty-four 

 individuals to see whether there was agreement in the relative sensi- 

 tiveness of their different tissues and the corresponding tissues of 

 vertebrates. As the largest animals Avere only three millimeters in 

 diameter and the whole length of the bod}^ was laid in the grooved 

 cover of the radium cell, all parts of the body, and thus all tissues, 

 received a nearly equal amount of radiations. The debated question 

 of the sensitiveness of the central nervous system was therefore put 

 to the test under especially favorable conditions with Allolohophora, 

 as it also was with Cambarus. 



Allolobophora foetida. 



For the exposure of Allolobophora a cell (Figure) was used three 

 millimeters in depth, two centimeters wide, and four centimeters 

 long, containing three hundred milligrams of impure radium of one 

 thousandth the strength of the pure bromide.^ The roof of the cell 

 was a very thin sheet (window) of aluminum, the upper surface of 



1 For the use of a part of this radium I am under deep obligation to Mr. Hugo 

 Lieber, who placed it at the disposal of Professor Mark for the purpose of aiding in 

 these investigations. To Dr. Theodore Lyman I wish to express my appreciation for 

 his kindness, not only in loaning radium, but also for advice in matters of radium 

 physics. 



