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SummaryAdult albino rabbits were implanted with 304 stainless steel discs and cylinders (rods) in the following sites: beneath periosteum of the anterior calvarium, under the masseter muscle of the left mandibular ramus and in the body of the sacrospinalis muscle. (1) The tissue reaction around the disc implants was compared with that observed around the cylinder implants through the study of histological sections. (2) The degree of reactions observed at the various sites was contrasted with that seen at the other sites. In all cases the muscle implants showed the greatest reaction. Discs showed many micro areas of tissue reaction randomly around their periphery. I n contrast all the rod shaped implants in muscle showed a greater reaction towards the ends than in the mid portion of the shaft (clubbing) but rods implanted at other sites did not show this phenomenon. The results show that much of the histological tissue reaction seen around muscle implants is really caused by mechanical trauma which must be differentiated from a non-compatibility reaction. It is important to choose a test site where mechanical trauma will be minimal (submasseteric site) and use an implant shape (discs) which will not produce clubbing.Biological materials used in medicine and dentistry have undergone much investigation over the last three decades. While much effort has been directed towards defining the mechanical characteristics of

Surgical blades were contaminated by doing incisional biopsies on DMBA-induced cheek pouch carcinomas in hamsters. Contaminated blades were then used to: (1) make cytologic smears; (2) make incisions in the mucosal surface of the lower lip; (3) make incisions in the ventral surface of the tongue; (4) make incisions in the untreated left cheek pouch; and (5) make incisions in the pre-shaved back. One group of animals was killed three hr post-surgery. The second group was killed seven wk post-surgery. Tissues were excised and processed for microscopic study. Malignant cells were found in many of the incision sites of animals from the first group. In the animals of the second group, several tumors growing from the transplanted tumor cells were observed in the incision sites of the lower lips and the tongue. None was observed in the incision sites of the left cheek pouch or the back. Cervical lymph node metastases were found in approximately 50% of the animals of the second group.

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