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-worm Allolobophora 
foetida and in the crayfish Cambarus affinis to 
the beta rays of radium. 
By E. D. Conepon. 
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 Allolobophora 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 were only three millimeters in 
diameter and the whole length of the body 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 Allolobophora, 
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 
1For 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. 
