A Collodion Sac for Use in Animal Experimentation.

Sanarelli (1891) is believed to have been the first to employ collodion sacs in animal experimentation. Subsequently, sacs of different types have been used in various in vivo experiments by a number of investigators (see bibliography). Alcohol-ether collodion was employed in each case for the preparation of the semipermeable membranes. In order to withstand the distorting effect of the intestinal movements, the collodion had to be of rather high concentration, with correspondingly low permeability. In undertaking the present work, it was felt that certain investigations could be made much more satisfactorily if sacs could be prepared that were more permeable and at the same time more rugged than those that had been previously described. According to Elford (1931), acetic-acid collodion membranes are not only of a higher order of permeability than those of alcohol-ether collodion, but they are also highly heteroporous. The use of this fragile material necessitated the finding of a practical support. Fouard (1909) impregnated wire gauze with collodion. This type of support was tried and was found to be highly practical. The description by Gates (1921) was used as the point of departure in trying to prepare a highly permeable yet sturdy modification of his type of sac. After a considerable number of failures, a satisfactory sac has been evolved which is quite different from that of Gates. However, many of his practices, particularly those concerning the handling of sacs, have been incorporated.