Unser Haushund: Eine Spitzmaus im Wolfspelz? - Wolf-Ekkehard ...

378were completely unable to raise their bodies throughout periods of more than a week. All of these dogs finally show moreor less shrunken and degenerate thigh areas. The most severely affected ones walk with the typically modified seal-likeeversion of the hind extremities which, as previously stated, is common among the first hybrid generation. Figure 71illustrates a back-cross litter.Although the numbers are not sufficiently large for definite conclusions, it does seem probable at present that thisdefective condition is hereditary in nature and quite like a dominant character in its mode of expression. A backcrossof the Dane-St. Bernard hybrid on a pure Dane mother has given but one successful result, and this a small litter ofonly six. Four of these died, from no fault in handling, within a few days after birth and only two survived tomaturity. Both of these were typically paralyzed soon after three months of age. With so few cases the result can onlymean that this peculiar paralysis may still occur in the back-cross on the Dane parent, but it gives no idea whatever ofthe proportions or frequency which might be found in a large series of such offspring.Several matings between F 1 hybrids have resulted in pregnancies, but all of them with two exceptions have beenresorbed, aborted or in some way lost before reaching full-term births.From one litter of eight second generation, or F 2 , Dane-St. Bernard progeny seven animals have lived to maturity. Thegrandparental characters are segregated or redistributed in these second generation animals in several suggestiveways, although the numbers, of course, permit of no analysis at present. There are long-haired St. Bernard patternsand short-haired Dane coats, various spotting combinations, and body forms resembling both ancestral stocks as is seenin Fig. 70.The point of particular interest is that a number of these second generation puppies after three months of age havesuffered the same paralysis of the hind extremity as was shown in the first hybrid generation. It also seems probable thatseveral of these have entirely escaped this unfortunate condition or else it has been expressed in an unrecognizablymild degree. It seems probable that there may be segregation and definite transmission of factors determining theparalysis. Only greater numbers can make the frequency in occurrence of the paralysis in this generation satisfactorilyclear.Finally, we may conclude that this particular combination between a simple giant type dog and a giant withsymptoms of acromegaly does seem to produce a peculiar complex in the progeny which causes all members of the firsthybrid generation to suffer a definite paralysis with subsequent loss of certain muscle groups in the hind extremities.The data at present available seem to indicate that this paralysis results from definitely inherited conditions, althoughit has not yet been possible to analyze the exact genetics concerned in the expression of the character.We have made only one cross between the giant Dane and the normally-sized but acromegalic bloodhound. Thiscombination gives a pronounced overgrowth and wrinkling of the skin on a giant animal in the first generation of hybrids,but here there has been no paralysis.Among human families there is known a condition of primary muscular atrophy which frequently affects definitemuscle groups and results in crippling and inability to walk. This disease occurs in families in such a way as to makeit seem probable that it may be hereditary in origin. The lameness in the dogs arises more suddenly than a muscularatrophy would appear and at the beginning of the paralysis the muscles are large and strong. Nervous degenerationsand paralyses are known in human beings which in some respects resemble the peculiar paralysis occurring in thedogs. It is hoped that within the near future an exact understanding of the nature of this defective state may become clear,and that such an understanding may aid in an analysis of the human conditions.In the meanwhile we may venture to suggest that the appearance of paralysis in these races of dogs, in which unstableand modified function of the glands of internal secretion quite probably exists, leads one to suspect that anunfavorable glandular complex is either primarily or secondarily responsible for the paralytic condition.The internal chemical constitution and the general modifications in human beings suffering with nervoussymptoms are now being quite widely recognized as intricate subjects which nevertheless are open to investigationand serious study from the constitutional standpoint. Any experimental analysis of the inheritance of such conditionsmust necessarily depend upon investigations on lower animal forms.