FREEMAN, W. J. 
DR. RODDIE; Have any intracellular recordings been made 
around this area? 
DR. FREEMAN: These cells are somewhat smaller than red 
blood cells; the average intracellular electrode is, let us say, one- 
tenth of one micron in diameter, and its irregular movement due 
to vibration in this circumstance is too great. The average cell 
which can be successfully recorded from is some hundred microns 
is diameter. 
DR. RODDIE: Even though it is difficult, until this type of re- 
cording is made, I do not think any conclusions can be drawn; the 
failure of external electrodes to show any independent electrical 
activity really does not mean very much. 
DR. FREEMAN: No, all it means is that the electrical activity 
cannot be recorded with our presently available technique; and what 
I am saying is that the electrical activity that can be recorded there 
is not generated by those cells. It comes from somewhere else, 
and this is the point that is important in applying doctrinaire thinking 
to these problems. I started off with the assumption that what I 
recorded there was generated by cells foundthere, and this was not 
so. This is what I would emphasize above all, that which is recorded 
in a given structure may not come from that structure. In the case 
of a reticular structure like this, it probably does not. I fully agree 
that there must be cellular changes there. I think they will be more 
likely found not with electrical recording, but with other types of 
recording such as optical density, impedance, or paramagnetic 
resonance. There are a number of such techniques which are just 
coming into possibility now, which I think will give far better ap- 
proachability to this structure. There are obviously changes oc- 
curring here which are related to temperature regulation. I do not 
think electrical recording is the way to analyze them. 
DR. STUART: It seems interesting that the^unit potentials re- 
corded from the nucleus field of Forel begin fifteen seconds or so 
after shivering has begun. One wonders whether the units are driving 
the shivering or whether the shivering isdrivingthe units, particu- 
larly since once shivering begins, and a characteristic rhythm is 
set up in a limb, there is a proprioceptive input to the cerebellum, 
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