2. Process according to claim 1 wherein the mechanical line pressure is individually applied across the width of the pelt indirectly through the pair of protecting surfaces at least at two corresponding longitudinally spaced apart points for cumulative squeezing and forcing of such fat rearwardly and away from the corresponding trailing end of the pelt during the advancing.

3. Process according to claim 1 for defatting animal pelts which comprises applying selectively mechanical line pressure across the width of a pair of longitudinally advancing superimposed substantially smooth protecting surfaces facing each other and having a tubular animal pelt longitudinally situated fur-side out in covered relation therebetween, and squeezing and forcing gradually and incrementally the adhering fat from the interior of the tubular pelt rearwardly and out from the corresponding trailing end of the pelt during such advancing under the mechanical line pressure.

4. Process according to claim 3 wheRein the mechanical line pressure is individually applied across the width of the pair of protecting surfaces at least at two corresponding longitudinally spaced apart points for cumulative squeezing and forcing of such fat rearwardly and out from the trailing end of the pelt during the advancing.

5. Process according to claim 3 wherein the longitudinally advancing pair of protecting surfaces is advanced in unison under substantially constant selective positive forward pulling force with the pelt stationarily situated therebetween, and the mechanical line pressure is substantially constant selective line pressure.

6. Process according to claim 3 wherein the fat squeezed and forced out from the trailing end of the pelt enters the area between the corresponding trailing portions of the pair of protecting surfaces thereat and is discharged substantially from between such trailing portions during continued advance of the pair of protecting surfaces under the mechanical line pressure.

7. Process according to claim 3 for defatting animal pelts which comprises advancing in unison under substantially constant positive forward pulling force along a longitudinal path a pair of superimposed substantially smooth and slippery elongated protecting surfaces inwardly facing each other and having a tubular animal pelt, which has been removed in substantially tubular form from the animal without longitudinal slitting open of the pelt, substantially stationarily and longitudinally situated fur-side out in covered relation therebetween, individually applying selectively substantially constant mechanical roller pressure across the width of the pair of protecting surfaces at least at two corresponding longitudinally spaced apart points along the path, squeezing and forcing gradually and incrementally the adhering fat from the interior of the tubular pelt rearwardly and out from the corresponding trailing end of the pelt and into the surrounding area between the corresponding trailing portions of such pair of protecting surfaces thereat during advance of the pair of protecting surfaces along the path under the applied mechanical roller pressure, and discharging substantially such fat from between such trailing portions during continued advance of the pair of protecting surfaces along the path under the applied mechanical roller pressure.

8. Process according to claim 7 wherein the tubular pelt is a mink pelt.

9. Process according to claim 7 wherein the mechanical roller pressure is applied by passing the pair of protecting surfaces between a corresponding pair of coacting pressure rollers at each of two longitudinally spaced apart points along the path.

10. Process according to claim 9 wherein attendant fat is continuously removed from the rollers.

11. Process according to claim 7 wherein the protecting surfaces are substantially fat-impervious and imperforate.

12. Process according to claim 7 for defatting animal pelts which comprises advancing in unison under substantially constant positive forward pulling force along a longitudinal path a pair of superimposed substantially smooth and sliperry elongated protecting surfaces inwardly facing each other and having a tubular animal pelt, which has been removed substantially intact in substantially tubular form from the animal without longitudinal slitting open of the pelt, substantially stationarily and longitudinally situated fur-side out in covered relation therebetween substantially intermediate the leading and trailing portions of such pair of protecting surfaces, individually applying selectively substantially constant mechanical roller pressure across the width of the pair of protecting surfaces at two corresponding longitudinally spaced apart points along the path having an intervening linear distance therebetween less than the corresponding length of the longitudinally situated tubular pelt by respectively moving a pair of coacting pressure rollers at each of such points from a non-engagement position to an operative eNgagement position, squeezing and forcing gradually and incrementally the adhering fat from the interior of the tubular pelt rearwardly and out from the corresponding trailing end of the pelt and into the surrounding area between the corresponding trailing portions of the pair of protecting surfaces thereat during advance of the pair of protecting surfaces along the path under the applied mechanical roller pressure, discharging substantially such fat from between such trailing portions onto the respective pairs of rollers during continued advance of the pair of protecting surfaces along the path under the applied mechanical roller pressure, individually releasing the mechanical roller pressure by respectively moving the pair of pressure rollers at each of such points from the operative engagement position to the non-engagement position upon corresponding advance therepast of the trailing portions of the pair of protective surfaces, and removing the discharge fat from the pressure rollers.

14. Apparatus according to claim 13 wherein at least two corresponding longitudinally spaced apart pairs of coacting pressure rollers are positioned operatively in the path.

15. Apparatus according to claim 13 wherein the conducting means for advancing the pair of protecting surfaces includes traction means for advancing the pair of protecting surfaces under substantially constant selective positive forward pulling force along the path, and the coacting pressure rollers are provided with means for exerting substantially constant selective roller pressure.

16. Apparatus according to claim 13 for defatting animal pelts which comprises a pair of pelt retainers each having a substantially smooth protecting surface and together being advanceable along a path in substantially superimposed relation with the protecting surfaces inwardly facing each other, affixing means for removably stationarily situating an animal pelt to be defatted in covered relation between such inwardly facing protecting surfaces during advance along the path, coacting pressure rollers positioned operatively in the path, and conducting means for advancing in unison the pair of retainers in such superimposed relation and the affixing means along the path and into operative pressure engagement of such retainers with the rollers to squeeze and force gradually and incrementally the adhering fat from the pelt stationarily situatable by the affixing means between the pair of protecting surfaces.

17. Apparatus according to claim 16 wherein at least two corresponding longitudinally spaced apart pairs of coacting pressure rollers are positioned operatively in the path.

18. Apparatus according to claim 16 wherein the conducting means for advancing the pair of retainers includes traction means for advancing the pair of retainers under substantially constant selective positive forward pulling force along the path, and the coacting pressure rollers are provided with means for exerting substantially constant selective roller pressure.

19. Apparatus according to claim 16 wherein distribution means are operatively provided adjacent the path for selectively distributing fat-absorbing particulate material thereacross.

20. Apparatus according to claim 16 wherein the protecting surfaces are substantially fat-impervious and imperforate.

21. Apparatus according to claim 16 wherein the conducting means for advancing the pair of retainers includes traction means for advancing in unison the pair of retainers under substantially constant selective positive forward pulling force along the path, two corresponding longitudinally spaced apart pairs of superimposed upper and lower coacting pressure rollers are positioned operatively in the path, the upper roller of the first roller pair in the path is arranged as an idler roller and the remaining three rollers are arranged as driven rollers, roller driving means are provided for driving the three driven rollers at a selective peripheral rotational speed corresponding to the linear speed of advance of the pair of retainers via the traction means along the path, each upper roller of a roller pair is mounted for displacement into and out of operative engagement relation with the respective lower roller and is correspondingly provided with means for displacing the upper roller into and out of such operative engagement relation and for exerting substantially constant selective roller pressure against the respective lower roller when displaced into operative engagement relation therewith, and sensing means are provided for controlling the displacement of each such upper roller in accord with the position along the path of the corresponding portion of the pair of retainers at which the pelt is to be situated to displace each such upper roller into such operative engagement relation and to exert such roller pressure substantially only during the advancing of the corresponding pelt-situating portion of the pair of retainers therebetween.

22. Apparatus according to claim 21 wherein the pelt retainers of said pair are of selective corresponding length arranged in superimposed relation for advancing along a corresponding endless path and having their leading end portions fixed together and their trailing end portions freely disposed, the affixing means for removably stationarily situating the pelt are fixedly positioned between such leading end portions, and the traction means are operatively connected to such leading end portions to advance in unison the pelt retainers with the fixing means fixedly positioned therebetween along the corresponding endless path.

23. Apparatus according to claim 22 wherein the pelt retainers of said pair include an upper pelt retainer advanceable along a first endless path and having a selective length bounded between a leading and a trailing end portion with the corresponding protecting surface thereof disposed on the outer side thereof and a lower pelt retainer advanceable along a second endless path and having a selective length bounded between a leading and a trailing end portion with the corresponding protecting surface thereof disposed on the outer side of the second endless path, the affixing means for removably stationarily situating the pelt are fixedly disposed at the leading end portion of the lower pelt retainer on the outer side of the second endless path, and the traction means are respectively operatively connected to the leading and trailing end portions of the upper pelt retainer and to the leading end portion of the lower pelt retainer to advance in unison the upper pelt retainer and the lower pelt retainer with the affixing means fixedly positioned thereat along such paths and in opposing superimposed relation between the coacting rollers.

24. Apparatus according to claim 17 for defatting pelts which comprises a longitudinal platform having a top guiding surface provided with an elongated fat discharge opening therethrough, a pair of substantially parallel endless traction means mounted operatively on said platform for linear travel in unison along an endless path in laterally spaced apart relation, each such traction means having a forward traction section along the top guiding surface and a return traction section substantially along the underside of the platform, a plurality of pairs of corresponding superimposed upper and lower pelt retainers of selective corresponding length respectively having their leading end portions fixed together and their trailing end portions freely disposed, the retainers of each pair having a substantially smooth and slippery protecting surface inwardly facing each other, affixing means fixedly positioned at the leading end portions of each retainer pair for removably stationarily situating an animal pelt to be defatted in covered relation between the inwardly facing protecting surfaces of such retainers, the pairs of retainers being arranged in longitudinally spaced apart relation and across the lateral space between the pair of parallel traction means and connected at their corresponding leading end portions onto both such traction means for displacement in a forward direction along the top guiding surface and in a return direction substantially along the underside of the platform, a first pair of superimposed coacting pressure rollers including a fixed position lower driven roller and a displaceable upper idler roller, a second pair of superimposed coacting pressure rollers including a fixed position lower driven roller and a displaceable upper driven roller, the first and second pairs of rollers being arranged in longitudinally spaced apart ordinal relation operatively crosswise of the forward traction sections in the lateral space therebetween at such discharge opening with the lower rollers below and the upper rollers above substantially the level of the forward traction sections, individual linear displacement means operatively positioned for displacing respectively each of the upper rollers into and out of operative engagement relation with the corresponding lower roller and individual pressure exerting means for exerting pressure respectivey on each of the upper rollers when in operative engagement relation with the corresponding lower roller, a pair of longitudinally spaced apart retainer follower sensing members operatively positioned at selective points respectively beyond the corresponding first and second pairs of rollers in the path of the retainers along the forward traction sections for sensing sequentially the movement of the leading and trailing end portions of each pair of superimposed retainers therepast and for actuating respectively the individual linear displacement means to displace the corresponding upper roller into operative engagement relation position when the leading end portions of a pair of retainers is sensed and to displace such upper roller out of operative engagement relation position when the trailing end portions of such pair of retainers is sensed and for actuating said individual pressure exerting means to exert pressure on such corresponding roller when in such operative engagement relation position, a pair of upper roller sensing members operatively positioned respectively at selective points in the paths of displacement of the corresponding upper rollers remote from the position of operative engagement relation with the corresponding lower rollers for actuating respectively the individual pressure exerting means to arrest such pressure when the corresponding upper roller is out of operative engagement relation position, and conjoint traction and roller driving means for driving in unison such traction means along the path under substantially constant selective positive forward pulling force at a substantially constant selective linear speed and such driven rollers at a corresponding substantially constant peripheral rotational speed in any position of displacement of such upper rollers.

25. Apparatus according to claim 24 wherein the affixing means include a pair of operatively positioned eye hooks for engaging the corresponding eye holes of the animal pelt for removably stationarily situating such pelt in covered reLation between the corresponding protecting surfaces of each retainer pair, and wherein the individual linear displacement means include corresponding individual pressure medium operable coacting piston-cylinder arrangements operatively connected respectively to such upper rollers, and the individual pressure exerting means include valve means operable for flowing pressure medium under constant pressure to a corresponding such piston-cylinder arrangement when the respective upper roller is displaced into operative engagement with the corresponding lower roller.

26. Apparatus according to claim 25 wherein a distributing hopper is operatively provided ahead of the first pair of coacting rollers adjacent the forward traction sections for selectively distributing fat-absorbing particulate material thereacross and onto the path of the pairs of retainers, wherein the protecting surfaces are substantially fat-impervious and imperforate, and wherein the lower rollers are provided with fat-scraper blades in operative wiping contact therewith.