1194 
MONITORING 
The incisions over the back and electrode site 
are closed with silk in a routine manner. The 
interface construction can then proceed as de- 
scribed in the first section. 
SUMMARY 
Transfer or conduction of electrical signals 
from one side of the skin to the other may be 
accomplished by percutaneous wiring. The key 
points to consider in a successful percutaneous 
system are : maintenance of an "infection free" 
interface and minimizing the adverse effects at 
the recording or stimulating electrode site. 
Maintenance of an "infection free" interface 
may be affected by minimizing wire slippage 
(in and out of the subcutaneous space) and 
minimizing the size of the fissure between the 
skin and wire (or anchor). The interface de- 
scribed in this text, designed with these two 
factors in mind, has been successfully employed 
in animal experiments which involved cats and 
rats. To date, it appears that the adverse effects 
occurring at the stimulating or recording elec- 
trode are primarily the result of mechanical 
trauma inflicted by the electrode. The Caldwell 
electrode has been found to be satisfactory for 
use in both recording and stimulating applica- 
tions. This electrode causes very little tissue 
damage (in many cases it may be considered 
negligible) and has been used in experiments 
involving animals and man for periods in ex- 
cess of one year without failure. Special care 
must be taken in connecting the electrode to the 
main lead wire because of the very fine wire 
used in the construction of the electrode. A 
technique has been developed to accomplish this 
connection which is suitable for surgical im- 
plantation. 
REFERENCES 
1. Morrison, S. J. Tissue reaction to three-ceramics of 
porous and non-porous structures. M.S. Thesis. Clem- 
son University, Clemson, South Carolina, 1971. 
2. Gibbons, D. F. personal communication. Case West- 
ern Reserve University, Cleveland, Ohio, 1971. 
3. Gibbons, D. F., Peckham, P. H., Martin, R. L. 
Vitreous carbon percutaneous electrodes for muscle 
stimulation. Accepted for publication in J. Biomed. 
Mater Res. Symposium No. 3, pp. 155-164, 1972. 
4. Miller, J. Problems related to the maintenance of 
chronic percutaneous electronic leads and catheters — 
application of porous ceramic devices. Presented at 
the Engineering Foundations Conference on Engi- 
neering in Medicine — Bioceramics, Henniker, New 
Hampshire, 1970. 
5. Gertler, R. a., Adler, A. G., Mortimer, J. T. An 
interface for passing lead wires through the skin 
of laboratory animals. IEEE Trans, on Biomedical 
Engineering, Vol BME-18, No. 1, pp. 72-73, 1971. 
6. Caldwell, C. W. A high strength platinum per- 
cutaneous electrode for chronic use. Ph.D. Thesis. 
Engineering Design Center Report No. EDC 4-70-30, 
Case Western Reserve University, Cleveland, Ohio, 
1970. 
7. Peckham, P. H. Design considerations in electrical 
stimulation of skeletal muscle. M.S. Thesis. Engi- 
neering Design Center Report No. 4-68-23, Case 
Western Reserve University, Cleveland, Ohio, 1968. 
8. Gertler, R. A., Mortimer, J. T., Martin, R. L. 
Effects of intramuscular stimulation on skeletal 
muscle. (Preparation). Case Western Reserve Uni- 
versity, Cleveland, Ohio. 1972. 
DISCUSSION 
N. P. Ching, St. Vincent's Hospital, New 
York: Can you tell us what is the duration of 
your implants, particularly when you took sam- 
ples for your pathology study of tissue reaction ? 
Chairman Franklin: Repeat the question 
please. 
Dr. Mortimer : He wanted to know how long 
we had had the implant in, or when we did the 
pathology on the stimulation. It was done five 
days post experiment. At this point one would 
see the phagocytic activity approximately at its 
peak, and that's what we were seeing here pri- 
marily. The other ones we've seen were cases 
of continuous stimulation for thirty days. The 
passive implants have run something like up 
to three months and that was included in the 
data. 
E. P. McCuTCHEON, University of Kentucky, 
Lexington, Ky. : We found this procedure a bit 
tedious for six or eight leads that we're bring- 
ing through, which already have connectors on 
them. You'd have to build it on-site and that's 
awkward. One thing we've been trying and had 
some initial success with is a nylon velour bag 
that we simply bury under the skin, close it 
over completely, and then go back in ten days 
to two weeks. You can window it, overlap the 
skin, and sew it down. Then you can go back 
