H. A. RAGAN, P. L. HACKETT, B. J. MCCLANAHAN AND W. J. CLARKE 
929 
ulocytes. If it's lymphocytic, of course, then it's 
a lymphocytic infiltration. 
Dr. Earl : Have you done any comparisons ? 
Dr. Ragan : You mean feeding? 
Dr. Earl: I'm particularly interested in 
bone marrow effects. 
Dr. Ragan: No, Marv Goldman might be 
able to, he could answer the part on the dogs. 
Dr. Earl: The question I'm really after is 
that I'm of the opinion that insults to the bone 
marrow on the pig are more serious than insults 
to the bone marrow of dogs, and I'm wondering 
if other people have found this to be true. 
Dr. Ragan: Dr. Goldman? 
Marvin Goldman, University of California, 
Davis: We had somewhat a similar finding 
from several hundred beagle dogs. 
Dr. Ragan : I think it is interesting that, al- 
though lymphatic leukemia or lymphosarcoma 
is supposedly the most commonly observed in 
swine, we have seen no cases in our control ani- 
mals. Our two cases in the controls have been 
granulocytic. 
J. W. Clayton, University of Wisconsin: 
First of all, I take the opportunity to congratu- 
late you on a very elegant design. My question 
has to do with the toxicological aspects of when 
you recorded, in the sense that the percentage of 
stillbirths was around 5%, and both (I think 
there were 25 and 5 in the two groups) were 
about the same. I wonder if the fetuses were ex- 
amined for any teratogenic effects, other than 
skeletal deformity? 
Dr. Ragan : No. They were not. These were 
just gross observations. 
Dr. Clayton: My next question relates to 
the conduct of the "no effect" level. It would ap- 
pear from your data that the dose was below 25 
microrads. Could you comment on that? 
Dr. Ragan : A "no effect"? I don't know that 
I believe that there is a "no effect" level. We are 
not able to show it with the life span of these 
animals at the doses we're using, with these 
rather gross assays. Now I'm certain that with 
more sophisticated techniques that differences 
(effects) can be shown, but this was essentially 
an "effect-no effect" type of study. 
Dr. Clayton : How about the idea that the 
Fl's and F2's within two generations had a 
slightly higher number of tumors of one type 
than the parents did, even though the dose was 
in about the same range ? 
Dr. Ragan: The Fl's and F2's have a 
slightly higher dose. They are, of course, ex- 
posed from in utero on. 
Dr. Clayton: Yes, but how would you ex- 
plain the context of dosage — all dosage as the 
rate of dosage or some other idea of dosage? 
Dr. Ragan : Are you speaking of accumu- 
lated dose or a dose rate? I think probably the 
dose rate is also important in this. 
Dr. Clayton : I'm not sure whether it was in 
the next to the last slide, the average rad dose 
to parents was about 10 to 20 and to offspring it 
was about 13 to 17 ; it would be about the same 
dosage as far as accumulated dose was con- 
cerned. 
Dr. Ragan : The time of appearance of these 
neoplasms in the F1-F2 has a mean of about 36 
months. Whereas, in the originals, it's up about 
70, which I think again points to a possible 
feedback mechanism in which these animals, 
the Fl's and F2's, are more severely involved. 
Also, their homeostatic mechanisms are proba- 
bly turned on a little more. 
