1206 
MONITORING 
a lot with dogs, but more recently have worked 
with primates and have placed a number of 
transmitters in chimpanzees. We have one 
chimp transmitting excellent data now for over 
a year. 
T. Reich, New York University, New 
York: To say that Tom's apparatus is elegant 
would be saying very little indeed. We have had 
a chance to speak with him about a flow trans- 
ducer which we're now developing and which 
may help overcome some of the problems that 
were presented here this afternoon. The unit 
that I'm talking about uses a permanent magnet 
so that many of the power problems will be 
eliminated. The major problem now that faces 
us rather is to document that we can keep these 
units from drifting and we hope that perhaps in 
the next three or four months that will be ac- 
complished also. I think that with that informa- 
tion there will be a long step forward. 
Dr. Fryer : Thank you. Yes I think that peo- 
ple of course have used in the past permanent 
magnets. I have had no experience so I really 
can't comment. I know that the polarization 
potentials that one gets at the electrodes of 
course causes serious problems but I think there 
is always room for improvements with new 
techniques. It may be possible to compensate for 
these potentials and possibly get good flow 
measurements that way. 
D. B. Jackson, Abbott Laboratories, North 
Chicago: What is your capsulating material 
that works so well for your hardware ? 
Dr. Fryer: People that have been around a 
few years, and involved with electronics, know 
that the vacuum tube had its essential com- 
ponents in a sealed glass container. Later, 
transistors often came with glass, although the 
recent plastic coated ones have, in effect, a glass 
coating on the components themselves. We've 
put all of the electronic parts inside a metal 
container and bring the leads through with the 
usual type of glass to metal seal using Kovar 
leads that come with crystal cans. The trans- 
ducer leads are sealed in Silastic. Recently we 
have been using stainless steel lead wires for 
the transducers to avoid corrosion problems 
and to eliminate lead breakage. 
